diff --git a/erpnext/accounts/doctype/bank_reconciliation_tool/bank_reconciliation_tool.py b/erpnext/accounts/doctype/bank_reconciliation_tool/bank_reconciliation_tool.py
index e7371fb..4211bd0 100644
--- a/erpnext/accounts/doctype/bank_reconciliation_tool/bank_reconciliation_tool.py
+++ b/erpnext/accounts/doctype/bank_reconciliation_tool/bank_reconciliation_tool.py
@@ -218,6 +218,8 @@
 	# updated clear date of all the vouchers based on the bank transaction
 	vouchers = json.loads(vouchers)
 	transaction = frappe.get_doc("Bank Transaction", bank_transaction_name)
+	company_account = frappe.db.get_value('Bank Account', transaction.bank_account, 'account')
+
 	if transaction.unallocated_amount == 0:
 		frappe.throw(_("This bank transaction is already fully reconciled"))
 	total_amount = 0
@@ -226,7 +228,7 @@
 		total_amount += get_paid_amount(frappe._dict({
 			'payment_document': voucher['payment_doctype'],
 			'payment_entry': voucher['payment_name'],
-		}), transaction.currency)
+		}), transaction.currency, company_account)
 
 	if total_amount > transaction.unallocated_amount:
 		frappe.throw(_("The Sum Total of Amounts of All Selected Vouchers Should be Less than the Unallocated Amount of the Bank Transaction"))
@@ -261,7 +263,7 @@
 	return matching
 
 def check_matching(bank_account, company, transaction, document_types):
-	# combine all types of vocuhers
+	# combine all types of vouchers
 	subquery = get_queries(bank_account, company, transaction, document_types)
 	filters = {
 			"amount": transaction.unallocated_amount,
@@ -343,13 +345,11 @@
 def get_je_matching_query(amount_condition, transaction):
 	# get matching journal entry query
 
+	# We have mapping at the bank level
+	# So one bank could have both types of bank accounts like asset and liability
+	# So cr_or_dr should be judged only on basis of withdrawal and deposit and not account type
 	company_account = frappe.get_value("Bank Account", transaction.bank_account, "account")
-	root_type = frappe.get_value("Account", company_account, "root_type")
-
-	if root_type == "Liability":
-		cr_or_dr = "debit" if transaction.withdrawal > 0 else "credit"
-	else:
-		cr_or_dr = "credit" if transaction.withdrawal > 0 else "debit"
+	cr_or_dr = "credit" if transaction.withdrawal > 0 else "debit"
 
 	return f"""
 
diff --git a/erpnext/accounts/doctype/bank_transaction/bank_transaction.py b/erpnext/accounts/doctype/bank_transaction/bank_transaction.py
index 4620087..44cea31 100644
--- a/erpnext/accounts/doctype/bank_transaction/bank_transaction.py
+++ b/erpnext/accounts/doctype/bank_transaction/bank_transaction.py
@@ -102,7 +102,7 @@
 		AND
 			bt.docstatus = 1""", (payment_entry.payment_document, payment_entry.payment_entry), as_dict=True)
 
-def get_paid_amount(payment_entry, currency):
+def get_paid_amount(payment_entry, currency, bank_account):
 	if payment_entry.payment_document in ["Payment Entry", "Sales Invoice", "Purchase Invoice"]:
 
 		paid_amount_field = "paid_amount"
@@ -115,7 +115,7 @@
 			payment_entry.payment_entry, paid_amount_field)
 
 	elif payment_entry.payment_document == "Journal Entry":
-		return frappe.db.get_value(payment_entry.payment_document, payment_entry.payment_entry, "total_credit")
+		return frappe.db.get_value('Journal Entry Account', {'parent': payment_entry.payment_entry, 'account': bank_account}, "sum(credit_in_account_currency)")
 
 	elif payment_entry.payment_document == "Expense Claim":
 		return frappe.db.get_value(payment_entry.payment_document, payment_entry.payment_entry, "total_amount_reimbursed")
diff --git a/erpnext/accounts/doctype/purchase_invoice/test_purchase_invoice.py b/erpnext/accounts/doctype/purchase_invoice/test_purchase_invoice.py
index aa2408e..cb18dd3 100644
--- a/erpnext/accounts/doctype/purchase_invoice/test_purchase_invoice.py
+++ b/erpnext/accounts/doctype/purchase_invoice/test_purchase_invoice.py
@@ -986,7 +986,7 @@
 
 		pi = make_purchase_invoice(item=item.name, qty=1, rate=100, do_not_save=True)
 		pi.set_posting_time = 1
-		pi.posting_date = '2019-03-15'
+		pi.posting_date = '2019-01-10'
 		pi.items[0].enable_deferred_expense = 1
 		pi.items[0].service_start_date = "2019-01-10"
 		pi.items[0].service_end_date = "2019-03-15"
diff --git a/erpnext/controllers/accounts_controller.py b/erpnext/controllers/accounts_controller.py
index 2c92820..c862774 100644
--- a/erpnext/controllers/accounts_controller.py
+++ b/erpnext/controllers/accounts_controller.py
@@ -184,6 +184,8 @@
 					frappe.throw(_("Row #{0}: Service Start Date cannot be greater than Service End Date").format(d.idx))
 				elif getdate(self.posting_date) > getdate(d.service_end_date):
 					frappe.throw(_("Row #{0}: Service End Date cannot be before Invoice Posting Date").format(d.idx))
+				elif getdate(self.posting_date) > getdate(d.service_start_date):
+					frappe.throw(_("Row #{0}: Service Start Date cannot be before Invoice Posting Date").format(d.idx))
 
 	def validate_invoice_documents_schedule(self):
 		self.validate_payment_schedule_dates()
diff --git a/erpnext/non_profit/doctype/membership/membership.py b/erpnext/non_profit/doctype/membership/membership.py
index beb38e2..f9b295a 100644
--- a/erpnext/non_profit/doctype/membership/membership.py
+++ b/erpnext/non_profit/doctype/membership/membership.py
@@ -409,7 +409,7 @@
 def set_expired_status():
 	frappe.db.sql("""
 		UPDATE
-			`tabMembership` SET `status` = 'Expired'
+			`tabMembership` SET `membership_status` = 'Expired'
 		WHERE
-			`status` not in ('Cancelled') AND `to_date` < %s
+			`membership_status` not in ('Cancelled') AND `to_date` < %s
 		""", (nowdate()))
diff --git a/erpnext/payroll/doctype/salary_slip/test_salary_slip.py b/erpnext/payroll/doctype/salary_slip/test_salary_slip.py
index 3052a2b..6e8fae0 100644
--- a/erpnext/payroll/doctype/salary_slip/test_salary_slip.py
+++ b/erpnext/payroll/doctype/salary_slip/test_salary_slip.py
@@ -171,6 +171,7 @@
 		salary_slip.end_date = month_end_date
 		salary_slip.save()
 		salary_slip.submit()
+		salary_slip.reload()
 
 		no_of_days = self.get_no_of_days()
 		days_in_month = no_of_days[0]
diff --git a/erpnext/projects/doctype/project/project.js b/erpnext/projects/doctype/project/project.js
index 31460f6..4f19bbd 100644
--- a/erpnext/projects/doctype/project/project.js
+++ b/erpnext/projects/doctype/project/project.js
@@ -59,22 +59,16 @@
 
 			frm.trigger('show_dashboard');
 		}
-		frm.events.set_buttons(frm);
+		frm.trigger("set_custom_buttons");
 	},
 
-	set_buttons: function(frm) {
+	set_custom_buttons: function(frm) {
 		if (!frm.is_new()) {
 			frm.add_custom_button(__('Duplicate Project with Tasks'), () => {
 				frm.events.create_duplicate(frm);
-			});
+			}, __("Actions"));
 
-			frm.add_custom_button(__('Completed'), () => {
-				frm.events.set_status(frm, 'Completed');
-			}, __('Set Status'));
-
-			frm.add_custom_button(__('Cancelled'), () => {
-				frm.events.set_status(frm, 'Cancelled');
-			}, __('Set Status'));
+			frm.trigger("set_project_status_button");
 
 
 			if (frappe.model.can_read("Task")) {
@@ -83,7 +77,7 @@
 						"project": frm.doc.name
 					};
 					frappe.set_route("List", "Task", "Gantt");
-				});
+				}, __("View"));
 
 				frm.add_custom_button(__("Kanban Board"), () => {
 					frappe.call('erpnext.projects.doctype.project.project.create_kanban_board_if_not_exists', {
@@ -91,13 +85,35 @@
 					}).then(() => {
 						frappe.set_route('List', 'Task', 'Kanban', frm.doc.project_name);
 					});
-				});
+				}, __("View"));
 			}
 		}
 
 
 	},
 
+	set_project_status_button: function(frm) {
+		frm.add_custom_button(__('Set Project Status'), () => {
+			let d = new frappe.ui.Dialog({
+				"title": __("Set Project Status"),
+				"fields": [
+					{
+						"fieldname": "status",
+						"fieldtype": "Select",
+						"label": "Status",
+						"reqd": 1,
+						"options": "Completed\nCancelled",
+					},
+				],
+				primary_action: function() {
+					frm.events.set_status(frm, d.get_values().status);
+					d.hide();
+				},
+				primary_action_label: __("Set Project Status")
+			}).show();
+		}, __("Actions"));
+	},
+
 	create_duplicate: function(frm) {
 		return new Promise(resolve => {
 			frappe.prompt('Project Name', (data) => {
@@ -117,7 +133,9 @@
 	set_status: function(frm, status) {
 		frappe.confirm(__('Set Project and all Tasks to status {0}?', [status.bold()]), () => {
 			frappe.xcall('erpnext.projects.doctype.project.project.set_project_status',
-				{project: frm.doc.name, status: status}).then(() => { /* page will auto reload */ });
+				{project: frm.doc.name, status: status}).then(() => {
+				frm.reload_doc();
+			});
 		});
 	},
 
diff --git a/erpnext/projects/report/project_profitability/test_project_profitability.py b/erpnext/projects/report/project_profitability/test_project_profitability.py
index 0415690..1eb3d0d 100644
--- a/erpnext/projects/report/project_profitability/test_project_profitability.py
+++ b/erpnext/projects/report/project_profitability/test_project_profitability.py
@@ -25,6 +25,7 @@
 
 		self.timesheet = make_timesheet(emp, is_billable=1)
 		self.salary_slip = make_salary_slip(self.timesheet.name)
+		self.salary_slip.start_date = self.timesheet.start_date
 
 		holidays = self.salary_slip.get_holidays_for_employee(date, date)
 		if holidays:
@@ -41,8 +42,8 @@
 	def test_project_profitability(self):
 		filters = {
 			'company': '_Test Company',
-			'start_date': add_days(getdate(), -3),
-			'end_date': getdate()
+			'start_date': add_days(self.timesheet.start_date, -3),
+			'end_date': self.timesheet.start_date
 		}
 
 		report = execute(filters)
diff --git a/erpnext/stock/doctype/serial_no/serial_no.json b/erpnext/stock/doctype/serial_no/serial_no.json
index a3d44af..6e1e0d4 100644
--- a/erpnext/stock/doctype/serial_no/serial_no.json
+++ b/erpnext/stock/doctype/serial_no/serial_no.json
@@ -1,7 +1,6 @@
 {
  "actions": [],
  "allow_import": 1,
- "allow_rename": 1,
  "autoname": "field:serial_no",
  "creation": "2013-05-16 10:59:15",
  "description": "Distinct unit of an Item",
@@ -434,10 +433,11 @@
  "icon": "fa fa-barcode",
  "idx": 1,
  "links": [],
- "modified": "2021-01-08 14:31:15.375996",
+ "modified": "2021-12-23 10:44:30.299450",
  "modified_by": "Administrator",
  "module": "Stock",
  "name": "Serial No",
+ "naming_rule": "By fieldname",
  "owner": "Administrator",
  "permissions": [
   {
@@ -476,5 +476,6 @@
  "show_name_in_global_search": 1,
  "sort_field": "modified",
  "sort_order": "DESC",
+ "states": [],
  "track_changes": 1
 }
\ No newline at end of file
diff --git a/erpnext/stock/doctype/serial_no/serial_no.py b/erpnext/stock/doctype/serial_no/serial_no.py
index 38291d1..2947faf 100644
--- a/erpnext/stock/doctype/serial_no/serial_no.py
+++ b/erpnext/stock/doctype/serial_no/serial_no.py
@@ -194,23 +194,6 @@
 		if sle_exists:
 			frappe.throw(_("Cannot delete Serial No {0}, as it is used in stock transactions").format(self.name))
 
-	def before_rename(self, old, new, merge=False):
-		if merge:
-			frappe.throw(_("Sorry, Serial Nos cannot be merged"))
-
-	def after_rename(self, old, new, merge=False):
-		"""rename serial_no text fields"""
-		for dt in frappe.db.sql("""select parent from tabDocField
-			where fieldname='serial_no' and fieldtype in ('Text', 'Small Text', 'Long Text')"""):
-
-			for item in frappe.db.sql("""select name, serial_no from `tab%s`
-				where serial_no like %s""" % (dt[0], frappe.db.escape('%' + old + '%'))):
-
-				serial_nos = map(lambda i: new if i.upper()==old.upper() else i, item[1].split('\n'))
-				frappe.db.sql("""update `tab%s` set serial_no = %s
-					where name=%s""" % (dt[0], '%s', '%s'),
-					('\n'.join(list(serial_nos)), item[0]))
-
 	def update_serial_no_reference(self, serial_no=None):
 		last_sle = self.get_last_sle(serial_no)
 		self.set_purchase_details(last_sle.get("purchase_sle"))
diff --git a/erpnext/stock/doctype/stock_entry/stock_entry.py b/erpnext/stock/doctype/stock_entry/stock_entry.py
index a00d63e..93e303c 100644
--- a/erpnext/stock/doctype/stock_entry/stock_entry.py
+++ b/erpnext/stock/doctype/stock_entry/stock_entry.py
@@ -35,10 +35,16 @@
 from erpnext.stock.utils import get_bin, get_incoming_rate
 
 
-class IncorrectValuationRateError(frappe.ValidationError): pass
-class DuplicateEntryForWorkOrderError(frappe.ValidationError): pass
-class OperationsNotCompleteError(frappe.ValidationError): pass
-class MaxSampleAlreadyRetainedError(frappe.ValidationError): pass
+class FinishedGoodError(frappe.ValidationError):
+	pass
+class IncorrectValuationRateError(frappe.ValidationError):
+	pass
+class DuplicateEntryForWorkOrderError(frappe.ValidationError):
+	pass
+class OperationsNotCompleteError(frappe.ValidationError):
+	pass
+class MaxSampleAlreadyRetainedError(frappe.ValidationError):
+	pass
 
 from erpnext.controllers.stock_controller import StockController
 
@@ -701,6 +707,11 @@
 
 			finished_item = self.get_finished_item()
 
+			if not finished_item and self.purpose == "Manufacture":
+				# In case of independent Manufacture entry, don't auto set
+				# user must decide and set
+				return
+
 			for d in self.items:
 				if d.t_warehouse and not d.s_warehouse:
 					if self.purpose=="Repack" or d.item_code == finished_item:
@@ -721,38 +732,64 @@
 		return finished_item
 
 	def validate_finished_goods(self):
-		"""validation: finished good quantity should be same as manufacturing quantity"""
-		if not self.work_order: return
+		"""
+			1. Check if FG exists
+			2. Check if Multiple FG Items are present
+			3. Check FG Item and Qty against WO if present
+		"""
+		production_item, wo_qty, finished_items = None, 0, []
 
-		production_item, wo_qty = frappe.db.get_value("Work Order",
-			self.work_order, ["production_item", "qty"])
+		wo_details = frappe.db.get_value(
+			"Work Order", self.work_order, ["production_item", "qty"]
+		)
+		if wo_details:
+			production_item, wo_qty = wo_details
 
-		finished_items = []
 		for d in self.get('items'):
 			if d.is_finished_item:
+				if not self.work_order:
+					finished_items.append(d.item_code)
+					continue # Independent Manufacture Entry, no WO to match against
+
 				if d.item_code != production_item:
 					frappe.throw(_("Finished Item {0} does not match with Work Order {1}")
-						.format(d.item_code, self.work_order))
+						.format(d.item_code, self.work_order)
+					)
 				elif flt(d.transfer_qty) > flt(self.fg_completed_qty):
-					frappe.throw(_("Quantity in row {0} ({1}) must be same as manufactured quantity {2}"). \
-						format(d.idx, d.transfer_qty, self.fg_completed_qty))
+					frappe.throw(_("Quantity in row {0} ({1}) must be same as manufactured quantity {2}")
+						.format(d.idx, d.transfer_qty, self.fg_completed_qty)
+					)
+
 				finished_items.append(d.item_code)
 
 		if len(set(finished_items)) > 1:
-			frappe.throw(_("Multiple items cannot be marked as finished item"))
+			frappe.throw(
+				msg=_("Multiple items cannot be marked as finished item"),
+				title=_("Note"),
+				exc=FinishedGoodError
+			)
 
 		if self.purpose == "Manufacture":
 			if not finished_items:
-				frappe.throw(_('Finished Good has not set in the stock entry {0}')
-					.format(self.name))
+				frappe.throw(
+					msg=_("There must be atleast 1 Finished Good in this Stock Entry").format(self.name),
+					title=_("Missing Finished Good"),
+					exc=FinishedGoodError
+				)
 
-			allowance_percentage = flt(frappe.db.get_single_value("Manufacturing Settings",
-				"overproduction_percentage_for_work_order"))
+			allowance_percentage = flt(
+				frappe.db.get_single_value(
+					"Manufacturing Settings","overproduction_percentage_for_work_order"
+				)
+			)
+			allowed_qty = wo_qty + ((allowance_percentage/100) * wo_qty)
 
-			allowed_qty = wo_qty + (allowance_percentage/100 * wo_qty)
-			if self.fg_completed_qty > allowed_qty:
-				frappe.throw(_("For quantity {0} should not be greater than work order quantity {1}")
-					.format(flt(self.fg_completed_qty), wo_qty))
+			# No work order could mean independent Manufacture entry, if so skip validation
+			if self.work_order and self.fg_completed_qty > allowed_qty:
+				frappe.throw(
+					_("For quantity {0} should not be greater than work order quantity {1}")
+					.format(flt(self.fg_completed_qty), wo_qty)
+				)
 
 	def update_stock_ledger(self):
 		sl_entries = []
diff --git a/erpnext/stock/doctype/stock_entry/test_stock_entry.py b/erpnext/stock/doctype/stock_entry/test_stock_entry.py
index 5a9e77e..b874874 100644
--- a/erpnext/stock/doctype/stock_entry/test_stock_entry.py
+++ b/erpnext/stock/doctype/stock_entry/test_stock_entry.py
@@ -15,7 +15,10 @@
 	set_item_variant_settings,
 )
 from erpnext.stock.doctype.serial_no.serial_no import *  # noqa
-from erpnext.stock.doctype.stock_entry.stock_entry import move_sample_to_retention_warehouse
+from erpnext.stock.doctype.stock_entry.stock_entry import (
+	FinishedGoodError,
+	move_sample_to_retention_warehouse,
+)
 from erpnext.stock.doctype.stock_entry.stock_entry_utils import make_stock_entry
 from erpnext.stock.doctype.stock_ledger_entry.stock_ledger_entry import StockFreezeError
 from erpnext.stock.doctype.stock_reconciliation.stock_reconciliation import (
@@ -929,6 +932,38 @@
 		distributed_costs = [d.additional_cost for d in se.items]
 		self.assertEqual([40.0, 60.0], distributed_costs)
 
+	def test_independent_manufacture_entry(self):
+		"Test FG items and incoming rate calculation in Maniufacture Entry without WO or BOM linked."
+		se = frappe.get_doc(
+			doctype="Stock Entry",
+			purpose="Manufacture",
+			stock_entry_type="Manufacture",
+			company="_Test Company",
+			items=[
+				frappe._dict(item_code="_Test Item", qty=1, basic_rate=200, s_warehouse="_Test Warehouse - _TC"),
+				frappe._dict(item_code="_Test FG Item", qty=4, t_warehouse="_Test Warehouse 1 - _TC")
+			]
+		)
+		# SE must have atleast one FG
+		self.assertRaises(FinishedGoodError, se.save)
+
+		se.items[0].is_finished_item = 1
+		se.items[1].is_finished_item = 1
+		# SE cannot have multiple FGs
+		self.assertRaises(FinishedGoodError, se.save)
+
+		se.items[0].is_finished_item = 0
+		se.save()
+
+		# Check if FG cost is calculated based on RM total cost
+		# RM total cost = 200, FG rate = 200/4(FG qty) =  50
+		self.assertEqual(se.items[1].basic_rate, 50)
+		self.assertEqual(se.value_difference, 0.0)
+		self.assertEqual(se.total_incoming_value, se.total_outgoing_value)
+
+		# teardown
+		se.delete()
+
 	@change_settings("Stock Settings", {"allow_negative_stock": 0})
 	def test_future_negative_sle(self):
 		# Initialize item, batch, warehouse, opening qty
diff --git a/erpnext/stock/report/stock_ageing/stock_ageing.py b/erpnext/stock/report/stock_ageing/stock_ageing.py
index 0ebe4f9..e6dfc97 100644
--- a/erpnext/stock/report/stock_ageing/stock_ageing.py
+++ b/erpnext/stock/report/stock_ageing/stock_ageing.py
@@ -3,6 +3,7 @@
 
 
 from operator import itemgetter
+from typing import Dict, List, Tuple, Union
 
 import frappe
 from frappe import _
@@ -10,19 +11,29 @@
 
 from erpnext.stock.doctype.serial_no.serial_no import get_serial_nos
 
+Filters = frappe._dict
 
-def execute(filters=None):
-	columns = get_columns(filters)
-	item_details = get_fifo_queue(filters)
+def execute(filters: Filters = None) -> Tuple:
 	to_date = filters["to_date"]
-	_func = itemgetter(1)
+	columns = get_columns(filters)
 
+	item_details = FIFOSlots(filters).generate()
+	data = format_report_data(filters, item_details, to_date)
+
+	chart_data = get_chart_data(data, filters)
+
+	return columns, data, None, chart_data
+
+def format_report_data(filters: Filters, item_details: Dict, to_date: str) -> List[Dict]:
+	"Returns ordered, formatted data with ranges."
+	_func = itemgetter(1)
 	data = []
+
 	for item, item_dict in item_details.items():
 		earliest_age, latest_age = 0, 0
+		details = item_dict["details"]
 
 		fifo_queue = sorted(filter(_func, item_dict["fifo_queue"]), key=_func)
-		details = item_dict["details"]
 
 		if not fifo_queue: continue
 
@@ -31,23 +42,22 @@
 		latest_age = date_diff(to_date, fifo_queue[-1][1])
 		range1, range2, range3, above_range3 = get_range_age(filters, fifo_queue, to_date, item_dict)
 
-		row = [details.name, details.item_name,
-			details.description, details.item_group, details.brand]
+		row = [details.name, details.item_name, details.description,
+			details.item_group, details.brand]
 
 		if filters.get("show_warehouse_wise_stock"):
 			row.append(details.warehouse)
 
 		row.extend([item_dict.get("total_qty"), average_age,
 			range1, range2, range3, above_range3,
-			earliest_age, latest_age, details.stock_uom])
+			earliest_age, latest_age,
+			details.stock_uom])
 
 		data.append(row)
 
-	chart_data = get_chart_data(data, filters)
+	return data
 
-	return columns, data, None, chart_data
-
-def get_average_age(fifo_queue, to_date):
+def get_average_age(fifo_queue: List, to_date: str) -> float:
 	batch_age = age_qty = total_qty = 0.0
 	for batch in fifo_queue:
 		batch_age = date_diff(to_date, batch[1])
@@ -61,7 +71,7 @@
 
 	return flt(age_qty / total_qty, 2) if total_qty else 0.0
 
-def get_range_age(filters, fifo_queue, to_date, item_dict):
+def get_range_age(filters: Filters, fifo_queue: List, to_date: str, item_dict: Dict) -> Tuple:
 	range1 = range2 = range3 = above_range3 = 0.0
 
 	for item in fifo_queue:
@@ -79,7 +89,7 @@
 
 	return range1, range2, range3, above_range3
 
-def get_columns(filters):
+def get_columns(filters: Filters) -> List[Dict]:
 	range_columns = []
 	setup_ageing_columns(filters, range_columns)
 	columns = [
@@ -164,106 +174,7 @@
 
 	return columns
 
-def get_fifo_queue(filters, sle=None):
-	item_details = {}
-	transferred_item_details = {}
-	serial_no_batch_purchase_details = {}
-
-	if sle == None:
-		sle = get_stock_ledger_entries(filters)
-
-	for d in sle:
-		key = (d.name, d.warehouse) if filters.get('show_warehouse_wise_stock') else d.name
-		item_details.setdefault(key, {"details": d, "fifo_queue": []})
-		fifo_queue = item_details[key]["fifo_queue"]
-
-		transferred_item_key = (d.voucher_no, d.name, d.warehouse)
-		transferred_item_details.setdefault(transferred_item_key, [])
-
-		if d.voucher_type == "Stock Reconciliation":
-			d.actual_qty = flt(d.qty_after_transaction) - flt(item_details[key].get("qty_after_transaction", 0))
-
-		serial_no_list = get_serial_nos(d.serial_no) if d.serial_no else []
-
-		if d.actual_qty > 0:
-			if transferred_item_details.get(transferred_item_key):
-				batch = transferred_item_details[transferred_item_key][0]
-				fifo_queue.append(batch)
-				transferred_item_details[transferred_item_key].pop(0)
-			else:
-				if serial_no_list:
-					for serial_no in serial_no_list:
-						if serial_no_batch_purchase_details.get(serial_no):
-							fifo_queue.append([serial_no, serial_no_batch_purchase_details.get(serial_no)])
-						else:
-							serial_no_batch_purchase_details.setdefault(serial_no, d.posting_date)
-							fifo_queue.append([serial_no, d.posting_date])
-				else:
-					fifo_queue.append([d.actual_qty, d.posting_date])
-		else:
-			if serial_no_list:
-				fifo_queue[:] = [serial_no for serial_no in fifo_queue if serial_no[0] not in serial_no_list]
-			else:
-				qty_to_pop = abs(d.actual_qty)
-				while qty_to_pop:
-					batch = fifo_queue[0] if fifo_queue else [0, None]
-					if 0 < flt(batch[0]) <= qty_to_pop:
-						# if batch qty > 0
-						# not enough or exactly same qty in current batch, clear batch
-						qty_to_pop -= flt(batch[0])
-						transferred_item_details[transferred_item_key].append(fifo_queue.pop(0))
-					else:
-						# all from current batch
-						batch[0] = flt(batch[0]) - qty_to_pop
-						transferred_item_details[transferred_item_key].append([qty_to_pop, batch[1]])
-						qty_to_pop = 0
-
-		item_details[key]["qty_after_transaction"] = d.qty_after_transaction
-
-		if "total_qty" not in item_details[key]:
-			item_details[key]["total_qty"] = d.actual_qty
-		else:
-			item_details[key]["total_qty"] += d.actual_qty
-
-		item_details[key]["has_serial_no"] = d.has_serial_no
-
-	return item_details
-
-def get_stock_ledger_entries(filters):
-	return frappe.db.sql("""select
-			item.name, item.item_name, item_group, brand, description, item.stock_uom, item.has_serial_no,
-			actual_qty, posting_date, voucher_type, voucher_no, serial_no, batch_no, qty_after_transaction, warehouse
-		from `tabStock Ledger Entry` sle,
-			(select name, item_name, description, stock_uom, brand, item_group, has_serial_no
-				from `tabItem` {item_conditions}) item
-		where item_code = item.name and
-			company = %(company)s and
-			posting_date <= %(to_date)s and
-			is_cancelled != 1
-			{sle_conditions}
-			order by posting_date, posting_time, sle.creation, actual_qty""" #nosec
-		.format(item_conditions=get_item_conditions(filters),
-			sle_conditions=get_sle_conditions(filters)), filters, as_dict=True)
-
-def get_item_conditions(filters):
-	conditions = []
-	if filters.get("item_code"):
-		conditions.append("item_code=%(item_code)s")
-	if filters.get("brand"):
-		conditions.append("brand=%(brand)s")
-
-	return "where {}".format(" and ".join(conditions)) if conditions else ""
-
-def get_sle_conditions(filters):
-	conditions = []
-	if filters.get("warehouse"):
-		lft, rgt = frappe.db.get_value('Warehouse', filters.get("warehouse"), ['lft', 'rgt'])
-		conditions.append("""warehouse in (select wh.name from `tabWarehouse` wh
-			where wh.lft >= {0} and rgt <= {1})""".format(lft, rgt))
-
-	return "and {}".format(" and ".join(conditions)) if conditions else ""
-
-def get_chart_data(data, filters):
+def get_chart_data(data: List, filters: Filters) -> Dict:
 	if not data:
 		return []
 
@@ -294,17 +205,201 @@
 		"type" : "bar"
 	}
 
-def setup_ageing_columns(filters, range_columns):
-	for i, label in enumerate(["0-{range1}".format(range1=filters["range1"]),
-		"{range1}-{range2}".format(range1=cint(filters["range1"])+ 1, range2=filters["range2"]),
-		"{range2}-{range3}".format(range2=cint(filters["range2"])+ 1, range3=filters["range3"]),
-		"{range3}-{above}".format(range3=cint(filters["range3"])+ 1, above=_("Above"))]):
-			add_column(range_columns, label="Age ("+ label +")", fieldname='range' + str(i+1))
+def setup_ageing_columns(filters: Filters, range_columns: List):
+	ranges = [
+		f"0 - {filters['range1']}",
+		f"{cint(filters['range1']) + 1} - {cint(filters['range2'])}",
+		f"{cint(filters['range2']) + 1} - {cint(filters['range3'])}",
+		f"{cint(filters['range3']) + 1} - {_('Above')}"
+	]
+	for i, label in enumerate(ranges):
+		fieldname = 'range' + str(i+1)
+		add_column(range_columns, label=f"Age ({label})",fieldname=fieldname)
 
-def add_column(range_columns, label, fieldname, fieldtype='Float', width=140):
+def add_column(range_columns: List, label:str, fieldname: str, fieldtype: str = 'Float', width: int = 140):
 	range_columns.append(dict(
 		label=label,
 		fieldname=fieldname,
 		fieldtype=fieldtype,
 		width=width
 	))
+
+
+class FIFOSlots:
+	"Returns FIFO computed slots of inwarded stock as per date."
+
+	def __init__(self, filters: Dict = None , sle: List = None):
+		self.item_details = {}
+		self.transferred_item_details = {}
+		self.serial_no_batch_purchase_details = {}
+		self.filters = filters
+		self.sle = sle
+
+	def generate(self) -> Dict:
+		"""
+			Returns dict of the foll.g structure:
+			Key = Item A / (Item A, Warehouse A)
+			Key: {
+				'details' -> Dict: ** item details **,
+				'fifo_queue' -> List: ** list of lists containing entries/slots for existing stock,
+					consumed/updated and maintained via FIFO. **
+			}
+		"""
+		if self.sle is None:
+			self.sle = self.__get_stock_ledger_entries()
+
+		for d in self.sle:
+			key, fifo_queue, transferred_item_key = self.__init_key_stores(d)
+
+			if d.voucher_type == "Stock Reconciliation":
+				prev_balance_qty = self.item_details[key].get("qty_after_transaction", 0)
+				d.actual_qty = flt(d.qty_after_transaction) - flt(prev_balance_qty)
+
+			serial_nos = get_serial_nos(d.serial_no) if d.serial_no else []
+
+			if d.actual_qty > 0:
+				self.__compute_incoming_stock(d, fifo_queue, transferred_item_key, serial_nos)
+			else:
+				self.__compute_outgoing_stock(d, fifo_queue, transferred_item_key, serial_nos)
+
+			self.__update_balances(d, key)
+
+		return self.item_details
+
+	def __init_key_stores(self, row: Dict) -> Tuple:
+		"Initialise keys and FIFO Queue."
+
+		key = (row.name, row.warehouse) if self.filters.get('show_warehouse_wise_stock') else row.name
+		self.item_details.setdefault(key, {"details": row, "fifo_queue": []})
+		fifo_queue = self.item_details[key]["fifo_queue"]
+
+		transferred_item_key = (row.voucher_no, row.name, row.warehouse)
+		self.transferred_item_details.setdefault(transferred_item_key, [])
+
+		return key, fifo_queue, transferred_item_key
+
+	def __compute_incoming_stock(self, row: Dict, fifo_queue: List, transfer_key: Tuple, serial_nos: List):
+		"Update FIFO Queue on inward stock."
+
+		if self.transferred_item_details.get(transfer_key):
+			# inward/outward from same voucher, item & warehouse
+			slot = self.transferred_item_details[transfer_key].pop(0)
+			fifo_queue.append(slot)
+		else:
+			if not serial_nos:
+				if fifo_queue and flt(fifo_queue[0][0]) < 0:
+					# neutralize negative stock by adding positive stock
+					fifo_queue[0][0] += flt(row.actual_qty)
+					fifo_queue[0][1] = row.posting_date
+				else:
+					fifo_queue.append([flt(row.actual_qty), row.posting_date])
+				return
+
+			for serial_no in serial_nos:
+				if self.serial_no_batch_purchase_details.get(serial_no):
+					fifo_queue.append([serial_no, self.serial_no_batch_purchase_details.get(serial_no)])
+				else:
+					self.serial_no_batch_purchase_details.setdefault(serial_no, row.posting_date)
+					fifo_queue.append([serial_no, row.posting_date])
+
+	def __compute_outgoing_stock(self, row: Dict, fifo_queue: List, transfer_key: Tuple, serial_nos: List):
+		"Update FIFO Queue on outward stock."
+		if serial_nos:
+			fifo_queue[:] = [serial_no for serial_no in fifo_queue if serial_no[0] not in serial_nos]
+			return
+
+		qty_to_pop = abs(row.actual_qty)
+		while qty_to_pop:
+			slot = fifo_queue[0] if fifo_queue else [0, None]
+			if 0 < flt(slot[0]) <= qty_to_pop:
+				# qty to pop >= slot qty
+				# if +ve and not enough or exactly same balance in current slot, consume whole slot
+				qty_to_pop -= flt(slot[0])
+				self.transferred_item_details[transfer_key].append(fifo_queue.pop(0))
+			elif not fifo_queue:
+				# negative stock, no balance but qty yet to consume
+				fifo_queue.append([-(qty_to_pop), row.posting_date])
+				self.transferred_item_details[transfer_key].append([row.actual_qty, row.posting_date])
+				qty_to_pop = 0
+			else:
+				# qty to pop < slot qty, ample balance
+				# consume actual_qty from first slot
+				slot[0] = flt(slot[0]) - qty_to_pop
+				self.transferred_item_details[transfer_key].append([qty_to_pop, slot[1]])
+				qty_to_pop = 0
+
+	def __update_balances(self, row: Dict, key: Union[Tuple, str]):
+		self.item_details[key]["qty_after_transaction"] = row.qty_after_transaction
+
+		if "total_qty" not in self.item_details[key]:
+			self.item_details[key]["total_qty"] = row.actual_qty
+		else:
+			self.item_details[key]["total_qty"] += row.actual_qty
+
+		self.item_details[key]["has_serial_no"] = row.has_serial_no
+
+	def __get_stock_ledger_entries(self) -> List[Dict]:
+		sle = frappe.qb.DocType("Stock Ledger Entry")
+		item = self.__get_item_query() # used as derived table in sle query
+
+		sle_query = (
+			frappe.qb.from_(sle).from_(item)
+			.select(
+				item.name, item.item_name, item.item_group,
+				item.brand, item.description,
+				item.stock_uom, item.has_serial_no,
+				sle.actual_qty, sle.posting_date,
+				sle.voucher_type, sle.voucher_no,
+				sle.serial_no, sle.batch_no,
+				sle.qty_after_transaction, sle.warehouse
+			).where(
+				(sle.item_code == item.name)
+				& (sle.company == self.filters.get("company"))
+				& (sle.posting_date <= self.filters.get("to_date"))
+				& (sle.is_cancelled != 1)
+			)
+		)
+
+		if self.filters.get("warehouse"):
+			sle_query = self.__get_warehouse_conditions(sle, sle_query)
+
+		sle_query = sle_query.orderby(
+			sle.posting_date, sle.posting_time, sle.creation, sle.actual_qty
+		)
+
+		return sle_query.run(as_dict=True)
+
+	def __get_item_query(self) -> str:
+		item_table = frappe.qb.DocType("Item")
+
+		item = frappe.qb.from_("Item").select(
+			"name", "item_name", "description", "stock_uom",
+			"brand", "item_group", "has_serial_no"
+		)
+
+		if self.filters.get("item_code"):
+			item = item.where(item_table.item_code == self.filters.get("item_code"))
+
+		if self.filters.get("brand"):
+			item = item.where(item_table.brand == self.filters.get("brand"))
+
+		return item
+
+	def __get_warehouse_conditions(self, sle, sle_query) -> str:
+		warehouse = frappe.qb.DocType("Warehouse")
+		lft, rgt = frappe.db.get_value(
+			"Warehouse",
+			self.filters.get("warehouse"),
+			['lft', 'rgt']
+		)
+
+		warehouse_results = (
+			frappe.qb.from_(warehouse)
+			.select("name").where(
+				(warehouse.lft >= lft)
+				& (warehouse.rgt <= rgt)
+			).run()
+		)
+		warehouse_results = [x[0] for x in warehouse_results]
+
+		return sle_query.where(sle.warehouse.isin(warehouse_results))
diff --git a/erpnext/stock/report/stock_ageing/stock_ageing_fifo_logic.md b/erpnext/stock/report/stock_ageing/stock_ageing_fifo_logic.md
new file mode 100644
index 0000000..5ffe97f
--- /dev/null
+++ b/erpnext/stock/report/stock_ageing/stock_ageing_fifo_logic.md
@@ -0,0 +1,73 @@
+### Concept of FIFO Slots
+
+Since we need to know age-wise remaining stock, we maintain all the inward entries as slots. So each time stock comes in, a slot is added for the same.
+
+Eg. For Item A:
+----------------------
+Date | Qty | Queue
+----------------------
+1st  | +50 | [[50, 1-12-2021]]
+2nd  | +20 | [[50, 1-12-2021], [20, 2-12-2021]]
+----------------------
+
+Now the queue can tell us the total stock and also how old the stock is.
+Here, the balance qty is 70.
+50 qty is (today-the 1st) days old
+20 qty is (today-the 2nd) days old
+
+### Calculation of FIFO Slots
+
+#### Case 1: Outward from sufficient balance qty
+----------------------
+Date | Qty | Queue
+----------------------
+1st  | +50 | [[50, 1-12-2021]]
+2nd  | -20 | [[30, 1-12-2021]]
+2nd  | +20 | [[30, 1-12-2021], [20, 2-12-2021]]
+
+Here after the first entry, while issuing 20 qty:
+- **since 20 is lesser than the balance**, **qty_to_pop (20)** is simply consumed from first slot (FIFO consumption)
+- Any inward entry after as usual will get its own slot added to the queue
+
+#### Case 2: Outward from sufficient cumulative (slots) balance qty
+----------------------
+Date | Qty | Queue
+----------------------
+1st  | +50 | [[50, 1-12-2021]]
+2nd  | +20 | [[50, 1-12-2021], [20, 2-12-2021]]
+2nd  | -60 | [[10, 2-12-2021]]
+
+- Consumption happens slot wise. First slot 1 is consumed
+- Since **qty_to_pop (60) is greater than slot 1 qty (50)**, the entire slot is consumed and popped
+- Now the queue is [[20, 2-12-2021]], and **qty_to_pop=10** (remaining qty to pop)
+- It then goes ahead to the next slot and consumes 10 from it
+- Now the queue is [[10, 2-12-2021]]
+
+#### Case 3: Outward from insufficient balance qty
+> This case is possible only if **Allow Negative Stock** was enabled at some point/is enabled.
+
+----------------------
+Date | Qty | Queue
+----------------------
+1st  | +50 | [[50, 1-12-2021]]
+2nd  | -60 | [[-10, 1-12-2021]]
+
+- Since **qty_to_pop (60)** is more than the balance in slot 1, the entire slot is consumed and popped
+- Now the queue is **empty**, and **qty_to_pop=10** (remaining qty to pop)
+- Since we still have more to consume, we append the balance since 60 is issued from 50 i.e. -10.
+- We register this negative value, since the stock issue has caused the balance to become negative
+
+Now when stock is inwarded:
+- Instead of adding a slot we check if there are any negative balances.
+- If yes, we keep adding positive stock to it until we make the balance positive.
+- Once the balance is positive, the next inward entry will add a new slot in the queue
+
+Eg:
+----------------------
+Date | Qty | Queue
+----------------------
+1st  | +50 | [[50, 1-12-2021]]
+2nd  | -60 | [[-10, 1-12-2021]]
+3rd  | +5  | [[-5, 3-12-2021]]
+4th  | +10 | [[5, 4-12-2021]]
+4th  | +20 | [[5, 4-12-2021], [20, 4-12-2021]]
\ No newline at end of file
diff --git a/erpnext/stock/report/stock_ageing/test_stock_ageing.py b/erpnext/stock/report/stock_ageing/test_stock_ageing.py
new file mode 100644
index 0000000..949bb7c
--- /dev/null
+++ b/erpnext/stock/report/stock_ageing/test_stock_ageing.py
@@ -0,0 +1,126 @@
+# Copyright (c) 2021, Frappe Technologies Pvt. Ltd. and Contributors
+# See license.txt
+
+import frappe
+
+from erpnext.stock.report.stock_ageing.stock_ageing import FIFOSlots
+from erpnext.tests.utils import ERPNextTestCase
+
+
+class TestStockAgeing(ERPNextTestCase):
+	def setUp(self) -> None:
+		self.filters = frappe._dict(
+			company="_Test Company",
+			to_date="2021-12-10"
+		)
+
+	def test_normal_inward_outward_queue(self):
+		"Reference: Case 1 in stock_ageing_fifo_logic.md"
+		sle = [
+			frappe._dict(
+				name="Flask Item",
+				actual_qty=30, qty_after_transaction=30,
+				posting_date="2021-12-01", voucher_type="Stock Entry",
+				voucher_no="001",
+				has_serial_no=False, serial_no=None
+			),
+			frappe._dict(
+				name="Flask Item",
+				actual_qty=20, qty_after_transaction=50,
+				posting_date="2021-12-02", voucher_type="Stock Entry",
+				voucher_no="002",
+				has_serial_no=False, serial_no=None
+			),
+			frappe._dict(
+				name="Flask Item",
+				actual_qty=(-10), qty_after_transaction=40,
+				posting_date="2021-12-03", voucher_type="Stock Entry",
+				voucher_no="003",
+				has_serial_no=False, serial_no=None
+			)
+		]
+
+		slots = FIFOSlots(self.filters, sle).generate()
+
+		self.assertTrue(slots["Flask Item"]["fifo_queue"])
+		result = slots["Flask Item"]
+		queue = result["fifo_queue"]
+
+		self.assertEqual(result["qty_after_transaction"], result["total_qty"])
+		self.assertEqual(queue[0][0], 20.0)
+
+	def test_insufficient_balance(self):
+		"Reference: Case 3 in stock_ageing_fifo_logic.md"
+		sle = [
+			frappe._dict(
+				name="Flask Item",
+				actual_qty=(-30), qty_after_transaction=(-30),
+				posting_date="2021-12-01", voucher_type="Stock Entry",
+				voucher_no="001",
+				has_serial_no=False, serial_no=None
+			),
+			frappe._dict(
+				name="Flask Item",
+				actual_qty=20, qty_after_transaction=(-10),
+				posting_date="2021-12-02", voucher_type="Stock Entry",
+				voucher_no="002",
+				has_serial_no=False, serial_no=None
+			),
+			frappe._dict(
+				name="Flask Item",
+				actual_qty=20, qty_after_transaction=10,
+				posting_date="2021-12-03", voucher_type="Stock Entry",
+				voucher_no="003",
+				has_serial_no=False, serial_no=None
+			),
+			frappe._dict(
+				name="Flask Item",
+				actual_qty=10, qty_after_transaction=20,
+				posting_date="2021-12-03", voucher_type="Stock Entry",
+				voucher_no="004",
+				has_serial_no=False, serial_no=None
+			)
+		]
+
+		slots = FIFOSlots(self.filters, sle).generate()
+
+		result = slots["Flask Item"]
+		queue = result["fifo_queue"]
+
+		self.assertEqual(result["qty_after_transaction"], result["total_qty"])
+		self.assertEqual(queue[0][0], 10.0)
+		self.assertEqual(queue[1][0], 10.0)
+
+	def test_stock_reconciliation(self):
+		sle = [
+			frappe._dict(
+				name="Flask Item",
+				actual_qty=30, qty_after_transaction=30,
+				posting_date="2021-12-01", voucher_type="Stock Entry",
+				voucher_no="001",
+				has_serial_no=False, serial_no=None
+			),
+			frappe._dict(
+				name="Flask Item",
+				actual_qty=0, qty_after_transaction=50,
+				posting_date="2021-12-02", voucher_type="Stock Reconciliation",
+				voucher_no="002",
+				has_serial_no=False, serial_no=None
+			),
+			frappe._dict(
+				name="Flask Item",
+				actual_qty=(-10), qty_after_transaction=40,
+				posting_date="2021-12-03", voucher_type="Stock Entry",
+				voucher_no="003",
+				has_serial_no=False, serial_no=None
+			)
+		]
+
+		slots = FIFOSlots(self.filters, sle).generate()
+
+		result = slots["Flask Item"]
+		queue = result["fifo_queue"]
+
+		self.assertEqual(result["qty_after_transaction"], result["total_qty"])
+		self.assertEqual(queue[0][0], 20.0)
+		self.assertEqual(queue[1][0], 20.0)
diff --git a/erpnext/stock/report/stock_balance/stock_balance.py b/erpnext/stock/report/stock_balance/stock_balance.py
index 3c7b26b..b4f43a7 100644
--- a/erpnext/stock/report/stock_balance/stock_balance.py
+++ b/erpnext/stock/report/stock_balance/stock_balance.py
@@ -9,7 +9,7 @@
 from frappe.utils import cint, date_diff, flt, getdate
 
 import erpnext
-from erpnext.stock.report.stock_ageing.stock_ageing import get_average_age, get_fifo_queue
+from erpnext.stock.report.stock_ageing.stock_ageing import FIFOSlots, get_average_age
 from erpnext.stock.report.stock_ledger.stock_ledger import get_item_group_condition
 from erpnext.stock.utils import add_additional_uom_columns, is_reposting_item_valuation_in_progress
 
@@ -33,7 +33,7 @@
 
 	if filters.get('show_stock_ageing_data'):
 		filters['show_warehouse_wise_stock'] = True
-		item_wise_fifo_queue = get_fifo_queue(filters, sle)
+		item_wise_fifo_queue = FIFOSlots(filters, sle).generate()
 
 	# if no stock ledger entry found return
 	if not sle:
diff --git a/erpnext/stock/report/warehouse_wise_item_balance_age_and_value/warehouse_wise_item_balance_age_and_value.py b/erpnext/stock/report/warehouse_wise_item_balance_age_and_value/warehouse_wise_item_balance_age_and_value.py
index 4d1491b..22bdb89 100644
--- a/erpnext/stock/report/warehouse_wise_item_balance_age_and_value/warehouse_wise_item_balance_age_and_value.py
+++ b/erpnext/stock/report/warehouse_wise_item_balance_age_and_value/warehouse_wise_item_balance_age_and_value.py
@@ -9,7 +9,7 @@
 from frappe import _
 from frappe.utils import flt
 
-from erpnext.stock.report.stock_ageing.stock_ageing import get_average_age, get_fifo_queue
+from erpnext.stock.report.stock_ageing.stock_ageing import FIFOSlots, get_average_age
 from erpnext.stock.report.stock_balance.stock_balance import (
 	get_item_details,
 	get_item_warehouse_map,
@@ -33,7 +33,7 @@
 	item_map = get_item_details(items, sle, filters)
 	iwb_map = get_item_warehouse_map(filters, sle)
 	warehouse_list = get_warehouse_list(filters)
-	item_ageing = get_fifo_queue(filters)
+	item_ageing = FIFOSlots(filters).generate()
 	data = []
 	item_balance = {}
 	item_value = {}