Merge pull request #21235 from mujeerhashmi/gstr_3b_report_fix

fix: GSTR 3B Report tax amount calculation
diff --git a/erpnext/regional/doctype/gstr_3b_report/gstr_3b_report.py b/erpnext/regional/doctype/gstr_3b_report/gstr_3b_report.py
index a2b32fe..9e7a023 100644
--- a/erpnext/regional/doctype/gstr_3b_report/gstr_3b_report.py
+++ b/erpnext/regional/doctype/gstr_3b_report/gstr_3b_report.py
@@ -277,7 +277,7 @@
 	def get_itc_details(self, reverse_charge='N'):
 
 		itc_amount = frappe.db.sql("""
-			select s.gst_category, sum(t.tax_amount) as tax_amount, t.account_head, s.eligibility_for_itc, s.reverse_charge
+			select s.gst_category, sum(t.tax_amount_after_discount_amount) as tax_amount, t.account_head, s.eligibility_for_itc, s.reverse_charge
 			from `tabPurchase Invoice` s , `tabPurchase Taxes and Charges` t
 			where s.docstatus = 1 and t.parent = s.name and s.reverse_charge = %s
 			and month(s.posting_date) = %s and year(s.posting_date) = %s and s.company = %s
@@ -312,7 +312,7 @@
 			and s.company = %s and s.company_gstin = %s and s.gst_category in ('Unregistered', 'Registered Composition', 'UIN Holders')
 			group by s.gst_category, s.place_of_supply""", (self.month_no, self.year, self.company, self.gst_details.get("gstin")), as_dict=1)
 
-		inter_state_supply_tax = frappe.db.sql(""" select sum(t.tax_amount) as tax_amount, s.place_of_supply, s.gst_category
+		inter_state_supply_tax = frappe.db.sql(""" select sum(t.tax_amount_after_discount_amount) as tax_amount, s.place_of_supply, s.gst_category
 			from `tabSales Invoice` s, `tabSales Taxes and Charges` t
 			where t.parent = s.name and s.docstatus = 1 and month(s.posting_date) = %s and year(s.posting_date) = %s
 			and s.company = %s and s.company_gstin = %s and s.gst_category in ('Unregistered', 'Registered Composition', 'UIN Holders')
@@ -385,7 +385,7 @@
 			tax_template = 'Purchase Taxes and Charges'
 
 		tax_amounts = frappe.db.sql("""
-			select s.gst_category, sum(t.tax_amount) as tax_amount, t.account_head
+			select s.gst_category, sum(t.tax_amount_after_discount_amount) as tax_amount, t.account_head
 			from `tab{doctype}` s , `tab{template}` t
 			where s.docstatus = 1 and t.parent = s.name and s.reverse_charge = %s
 			and month(s.posting_date) = %s and year(s.posting_date) = %s and s.company = %s