fix: Additional discount calculations in Invoices (#26553)

* fix: Additional discount calculations in Invoices

* revert: Client side handling for Dynamic GST Rates

* fix: Add update item tax template method back

* fix: Revert refresh field

* fix: add company change trigger
diff --git a/erpnext/public/js/controllers/taxes_and_totals.js b/erpnext/public/js/controllers/taxes_and_totals.js
index 52efbb5..53d5278 100644
--- a/erpnext/public/js/controllers/taxes_and_totals.js
+++ b/erpnext/public/js/controllers/taxes_and_totals.js
@@ -65,28 +65,23 @@
 		this.frm.refresh_fields();
 	},
 
-	calculate_discount_amount: function(){
+	calculate_discount_amount: function() {
 		if (frappe.meta.get_docfield(this.frm.doc.doctype, "discount_amount")) {
-			this.calculate_item_values();
-			this.calculate_net_total();
 			this.set_discount_amount();
 			this.apply_discount_amount();
 		}
 	},
 
 	_calculate_taxes_and_totals: function() {
-		frappe.run_serially([
-			() => this.validate_conversion_rate(),
-			() => this.calculate_item_values(),
-			() => this.update_item_tax_map(),
-			() => this.initialize_taxes(),
-			() => this.determine_exclusive_rate(),
-			() => this.calculate_net_total(),
-			() => this.calculate_taxes(),
-			() => this.manipulate_grand_total_for_inclusive_tax(),
-			() => this.calculate_totals(),
-			() => this._cleanup()
-		]);
+		this.validate_conversion_rate();
+		this.calculate_item_values();
+		this.initialize_taxes();
+		this.determine_exclusive_rate();
+		this.calculate_net_total();
+		this.calculate_taxes();
+		this.manipulate_grand_total_for_inclusive_tax();
+		this.calculate_totals();
+		this._cleanup();
 	},
 
 	validate_conversion_rate: function() {
@@ -107,7 +102,7 @@
 	},
 
 	calculate_item_values: function() {
-		var me = this;
+		let me = this;
 		if (!this.discount_amount_applied) {
 			$.each(this.frm.doc["items"] || [], function(i, item) {
 				frappe.model.round_floats_in(item);
@@ -268,46 +263,6 @@
 		frappe.model.round_floats_in(this.frm.doc, ["total", "base_total", "net_total", "base_net_total"]);
 	},
 
-	update_item_tax_map: function() {
-		let me = this;
-		let item_codes = [];
-		let item_rates = {};
-		let item_tax_templates = {};
-
-		$.each(this.frm.doc.items || [], function(i, item) {
-			if (item.item_code) {
-				// Use combination of name and item code in case same item is added multiple times
-				item_codes.push([item.item_code, item.name]);
-				item_rates[item.name] = item.net_rate;
-				item_tax_templates[item.name] = item.item_tax_template;
-			}
-		});
-
-		if (item_codes.length) {
-			return this.frm.call({
-				method: "erpnext.stock.get_item_details.get_item_tax_info",
-				args: {
-					company: me.frm.doc.company,
-					tax_category: cstr(me.frm.doc.tax_category),
-					item_codes: item_codes,
-					item_rates: item_rates,
-					item_tax_templates: item_tax_templates
-				},
-				callback: function(r) {
-					if (!r.exc) {
-						$.each(me.frm.doc.items || [], function(i, item) {
-							if (item.name && r.message.hasOwnProperty(item.name) && r.message[item.name].item_tax_template) {
-								item.item_tax_template = r.message[item.name].item_tax_template;
-								item.item_tax_rate = r.message[item.name].item_tax_rate;
-								me.add_taxes_from_item_tax_template(item.item_tax_rate);
-							}
-						});
-					}
-				}
-			});
-		}
-	},
-
 	add_taxes_from_item_tax_template: function(item_tax_map) {
 		let me = this;
 
@@ -632,8 +587,6 @@
 				tax.item_wise_tax_detail = JSON.stringify(tax.item_wise_tax_detail);
 			});
 		}
-
-		this.frm.refresh_fields();
 	},
 
 	set_discount_amount: function() {
diff --git a/erpnext/public/js/controllers/transaction.js b/erpnext/public/js/controllers/transaction.js
index b3af3d6..5475383 100644
--- a/erpnext/public/js/controllers/transaction.js
+++ b/erpnext/public/js/controllers/transaction.js
@@ -826,9 +826,9 @@
 
 				frappe.run_serially([
 					() => me.frm.script_manager.trigger("currency"),
+					() => me.update_item_tax_map(),
 					() => me.apply_default_taxes(),
-					() => me.apply_pricing_rule(),
-					() => me.calculate_taxes_and_totals()
+					() => me.apply_pricing_rule()
 				]);
 			}
 		}
@@ -1787,6 +1787,46 @@
 		]);
 	},
 
+	update_item_tax_map: function() {
+		let me = this;
+		let item_codes = [];
+		let item_rates = {};
+		let item_tax_templates = {};
+
+		$.each(this.frm.doc.items || [], function(i, item) {
+			if (item.item_code) {
+				// Use combination of name and item code in case same item is added multiple times
+				item_codes.push([item.item_code, item.name]);
+				item_rates[item.name] = item.net_rate;
+				item_tax_templates[item.name] = item.item_tax_template;
+			}
+		});
+
+		if (item_codes.length) {
+			return this.frm.call({
+				method: "erpnext.stock.get_item_details.get_item_tax_info",
+				args: {
+					company: me.frm.doc.company,
+					tax_category: cstr(me.frm.doc.tax_category),
+					item_codes: item_codes,
+					item_rates: item_rates,
+					item_tax_templates: item_tax_templates
+				},
+				callback: function(r) {
+					if (!r.exc) {
+						$.each(me.frm.doc.items || [], function(i, item) {
+							if (item.name && r.message.hasOwnProperty(item.name) && r.message[item.name].item_tax_template) {
+								item.item_tax_template = r.message[item.name].item_tax_template;
+								item.item_tax_rate = r.message[item.name].item_tax_rate;
+								me.add_taxes_from_item_tax_template(item.item_tax_rate);
+							}
+						});
+					}
+				}
+			});
+		}
+	},
+
 	item_tax_template: function(doc, cdt, cdn) {
 		var me = this;
 		if(me.frm.updating_party_details) return;