fix: get total without rounding off tax amounts for distributing discount (backport #47155)

Co-authored-by: Sagar Vora <16315650+sagarvora@users.noreply.github.com>

erpnext/accounts/doctype/purchase_invoice/test_purchase_invoice.py

@@ -2688,13 +2688,13 @@ class TestPurchaseInvoice(FrappeTestCase, StockTestMixin):
 		To test if after applying discount on grand total,
 		the grand total is calculated correctly without any rounding errors
 		"""
-		invoice = make_purchase_invoice(qty=2, rate=100, do_not_save=True, do_not_submit=True)
+		invoice = make_purchase_invoice(qty=3, rate=100, do_not_save=True, do_not_submit=True)
 		invoice.append(
 			"items",
 			{
 				"item_code": "_Test Item",
-				"qty": 1,
+				"qty": 3,
-				"rate": 21.39,
+				"rate": 50.3,
 			},
 		)
 		invoice.append(
@@ -2703,18 +2703,19 @@ class TestPurchaseInvoice(FrappeTestCase, StockTestMixin):
 				"charge_type": "On Net Total",
 				"account_head": "_Test Account VAT - _TC",
 				"description": "VAT",
-				"rate": 15.5,
+				"rate": 15,
 			},
 		)
 
-		# the grand total here will be 255.71
+		# the grand total here will be 518.54
 		invoice.disable_rounded_total = 1
-		# apply discount on grand total to adjust the grand total to 255
+		# apply discount on grand total to adjust the grand total to 518
-		invoice.discount_amount = 0.71
+		invoice.discount_amount = 0.54
+
 		invoice.save()
 
-		# check if grand total is 496 and not something like 254.99 due to rounding errors
+		# check if grand total is 518 and not something like 517.99 due to rounding errors
-		self.assertEqual(invoice.grand_total, 255)
+		self.assertEqual(invoice.grand_total, 518)
 
 	def test_apply_discount_on_grand_total_with_previous_row_total_tax(self):
 		"""

erpnext/controllers/taxes_and_totals.py

@@ -377,20 +377,22 @@ class calculate_taxes_and_totals:
 			self._calculate()
 
 	def calculate_taxes(self):
-		self.grand_total_diff = 0
+		doc = self.doc
+		if not doc.get("taxes"):
+			return
 
 		# maintain actual tax rate based on idx
 		actual_tax_dict = dict(
 			[
 				[tax.idx, flt(tax.tax_amount, tax.precision("tax_amount"))]
-				for tax in self.doc.get("taxes")
+				for tax in doc.taxes
 				if tax.charge_type == "Actual"
 			]
 		)
 
 		for n, item in enumerate(self._items):
 			item_tax_map = self._load_item_tax_rate(item.item_tax_rate)
-			for i, tax in enumerate(self.doc.get("taxes")):
+			for i, tax in enumerate(doc.taxes):
 				# tax_amount represents the amount of tax for the current step
 				current_tax_amount = self.get_current_tax_amount(item, tax, item_tax_map)
 				if frappe.flags.round_row_wise_tax:
@@ -425,30 +427,39 @@ class calculate_taxes_and_totals:
 					tax.grand_total_for_current_item = flt(item.net_amount + current_tax_amount)
 				else:
 					tax.grand_total_for_current_item = flt(
-						self.doc.get("taxes")[i - 1].grand_total_for_current_item + current_tax_amount
+						doc.taxes[i - 1].grand_total_for_current_item + current_tax_amount
 					)
 
-				# set precision in the last item iteration
+		discount_amount_applied = self.discount_amount_applied
-				if n == len(self._items) - 1:
+		if doc.apply_discount_on == "Grand Total" and (
-					self.round_off_totals(tax)
+			discount_amount_applied or doc.discount_amount or doc.additional_discount_percentage
-					self._set_in_company_currency(tax, ["tax_amount", "tax_amount_after_discount_amount"])
+		):
+			tax_amount_precision = doc.taxes[0].precision("tax_amount")
 
-					self.round_off_base_values(tax)
+			for i, tax in enumerate(doc.taxes):
-					self.set_cumulative_total(i, tax)
+				if discount_amount_applied:
+					tax.tax_amount_after_discount_amount = flt(
+						tax.tax_amount_after_discount_amount, tax_amount_precision
+					)
 
-					self._set_in_company_currency(tax, ["total"])
+				self.set_cumulative_total(i, tax)
 
-					# adjust Discount Amount loss in last tax iteration
+			if not discount_amount_applied:
-					if (
+				self.grand_total_for_distributing_discount = doc.taxes[-1].total
-						i == (len(self.doc.get("taxes")) - 1)
+			else:
-						and self.discount_amount_applied
+				self.grand_total_diff = flt(
-						and self.doc.discount_amount
+					self.grand_total_for_distributing_discount - doc.discount_amount - doc.taxes[-1].total,
-						and self.doc.apply_discount_on == "Grand Total"
+					doc.precision("grand_total"),
-					):
+				)
-						self.grand_total_diff = flt(
+
-							self.doc.grand_total - flt(self.doc.discount_amount) - tax.total,
+		for i, tax in enumerate(doc.taxes):
-							self.doc.precision("rounding_adjustment"),
+			self.round_off_totals(tax)
-						)
+			self._set_in_company_currency(tax, ["tax_amount", "tax_amount_after_discount_amount"])
+
+			self.round_off_base_values(tax)
+			self.set_cumulative_total(i, tax)
+
+			self._set_in_company_currency(tax, ["total"])
 
 	def get_tax_amount_if_for_valuation_or_deduction(self, tax_amount, tax):
 		# if just for valuation, do not add the tax amount in total
@@ -571,16 +582,20 @@ class calculate_taxes_and_totals:
 
 			if diff and abs(diff) <= (5.0 / 10 ** last_tax.precision("tax_amount")):
 				self.grand_total_diff = diff
+			else:
+				self.grand_total_diff = 0
 
 	def calculate_totals(self):
+		grand_total_diff = getattr(self, "grand_total_diff", 0)
+
 		if self.doc.get("taxes"):
-			self.doc.grand_total = flt(self.doc.get("taxes")[-1].total) + self.grand_total_diff
+			self.doc.grand_total = flt(self.doc.get("taxes")[-1].total) + grand_total_diff
 		else:
 			self.doc.grand_total = flt(self.doc.net_total)
 
 		if self.doc.get("taxes"):
 			self.doc.total_taxes_and_charges = flt(
-				self.doc.grand_total - self.doc.net_total - self.grand_total_diff,
+				self.doc.grand_total - self.doc.net_total - grand_total_diff,
 				self.doc.precision("total_taxes_and_charges"),
 			)
 		else:
@@ -725,7 +740,8 @@ class calculate_taxes_and_totals:
 			self.doc.base_discount_amount = 0
 
 	def get_total_for_discount_amount(self):
-		if self.doc.apply_discount_on == "Net Total":
+		doc = self.doc
+		if doc.apply_discount_on == "Net Total" or not doc.get("taxes"):
 			return self.doc.net_total
 
 		total_actual_tax = 0
@@ -745,7 +761,7 @@ class calculate_taxes_and_totals:
 				"cumulative_tax_amount": total_actual_tax,
 			}
 
-		for tax in self.doc.get("taxes"):
+		for tax in doc.taxes:
 			if tax.charge_type in ["Actual", "On Item Quantity"]:
 				update_actual_tax_dict(tax, tax.tax_amount)
 				continue
@@ -764,7 +780,7 @@ class calculate_taxes_and_totals:
 			)
 			update_actual_tax_dict(tax, base_tax_amount * tax.rate / 100)
 
-		return self.doc.grand_total - total_actual_tax
+		return getattr(self, "grand_total_for_distributing_discount", doc.grand_total) - total_actual_tax
 
 	def calculate_total_advance(self):
 		if not self.doc.docstatus.is_cancelled():

erpnext/public/js/controllers/taxes_and_totals.js

@@ -342,12 +342,14 @@ erpnext.taxes_and_totals = class TaxesAndTotals extends erpnext.payments {
 	}
 
 	calculate_taxes() {
+		const doc = this.frm.doc;
+		if (!doc.taxes?.length) return;
+
 		var me = this;
-		this.grand_total_diff = 0;
 		var actual_tax_dict = {};
 
 		// maintain actual tax rate based on idx
-		$.each(this.frm.doc["taxes"] || [], function(i, tax) {
+		$.each(doc.taxes, function(i, tax) {
 			if (tax.charge_type == "Actual") {
 				actual_tax_dict[tax.idx] = flt(tax.tax_amount, precision("tax_amount", tax));
 			}
@@ -355,7 +357,7 @@ erpnext.taxes_and_totals = class TaxesAndTotals extends erpnext.payments {
 
 		$.each(this.frm._items || [], function(n, item) {
 			var item_tax_map = me._load_item_tax_rate(item.item_tax_rate);
-			$.each(me.frm.doc["taxes"] || [], function(i, tax) {
+			$.each(doc.taxes, function(i, tax) {
 				// tax_amount represents the amount of tax for the current step
 				var current_tax_amount = me.get_current_tax_amount(item, tax, item_tax_map);
 				if (frappe.flags.round_row_wise_tax) {
@@ -400,29 +402,40 @@ erpnext.taxes_and_totals = class TaxesAndTotals extends erpnext.payments {
 					tax.grand_total_for_current_item =
 						flt(me.frm.doc["taxes"][i-1].grand_total_for_current_item + current_tax_amount);
 				}
-
-				// set precision in the last item iteration
-				if (n == me.frm._items.length - 1) {
-					me.round_off_totals(tax);
-					me.set_in_company_currency(tax,
-						["tax_amount", "tax_amount_after_discount_amount"]);
-
-					me.round_off_base_values(tax);
-
-					// in tax.total, accumulate grand total for each item
-					me.set_cumulative_total(i, tax);
-
-					me.set_in_company_currency(tax, ["total"]);
-
-					// adjust Discount Amount loss in last tax iteration
-					if ((i == me.frm.doc["taxes"].length - 1) && me.discount_amount_applied
-						&& me.frm.doc.apply_discount_on == "Grand Total" && me.frm.doc.discount_amount) {
-						me.grand_total_diff = flt(me.frm.doc.grand_total -
-							flt(me.frm.doc.discount_amount) - tax.total, precision("rounding_adjustment"));
-					}
-				}
 			});
 		});
+
+		const discount_amount_applied = this.discount_amount_applied;
+		if (doc.apply_discount_on === "Grand Total" && (discount_amount_applied || doc.discount_amount || doc.additional_discount_percentage)) {
+			const tax_amount_precision = precision("tax_amount", doc.taxes[0]);
+
+			for (const [i, tax] of doc.taxes.entries()) {
+				if (discount_amount_applied)
+					tax.tax_amount_after_discount_amount = flt(tax.tax_amount_after_discount_amount, tax_amount_precision);
+
+				this.set_cumulative_total(i, tax);
+			}
+
+			if (!this.discount_amount_applied) {
+				this.grand_total_for_distributing_discount = doc.taxes[doc.taxes.length - 1].total;
+			} else {
+				this.grand_total_diff = flt(
+					this.grand_total_for_distributing_discount - doc.discount_amount - doc.taxes[doc.taxes.length - 1].total, precision("grand_total"));
+			}
+		}
+
+		for (const [i, tax] of doc.taxes.entries()) {
+			me.round_off_totals(tax);
+			me.set_in_company_currency(tax,
+				["tax_amount", "tax_amount_after_discount_amount"]);
+
+			me.round_off_base_values(tax);
+
+			// in tax.total, accumulate grand total for each tax
+			me.set_cumulative_total(i, tax);
+
+			me.set_in_company_currency(tax, ["total"]);
+		}
 	}
 
 	set_cumulative_total(row_idx, tax) {
@@ -571,10 +584,12 @@ erpnext.taxes_and_totals = class TaxesAndTotals extends erpnext.payments {
 
 	calculate_totals() {
 		// Changing sequence can cause rounding_adjustmentng issue and on-screen discrepency
-		var me = this;
+		const me = this;
-		var tax_count = this.frm.doc["taxes"] ? this.frm.doc["taxes"].length : 0;
+		const tax_count = this.frm.doc.taxes?.length;
+		const grand_total_diff = this.grand_total_diff || 0;
+
 		this.frm.doc.grand_total = flt(tax_count
-			? this.frm.doc["taxes"][tax_count - 1].total + this.grand_total_diff
+			? this.frm.doc["taxes"][tax_count - 1].total + grand_total_diff
 			: this.frm.doc.net_total);
 
 		if(["Quotation", "Sales Order", "Delivery Note", "Sales Invoice", "POS Invoice"].includes(this.frm.doc.doctype)) {
@@ -606,7 +621,7 @@ erpnext.taxes_and_totals = class TaxesAndTotals extends erpnext.payments {
 		}
 
 		this.frm.doc.total_taxes_and_charges = flt(this.frm.doc.grand_total - this.frm.doc.net_total
-			- this.grand_total_diff, precision("total_taxes_and_charges"));
+			- grand_total_diff, precision("total_taxes_and_charges"));
 
 		this.set_in_company_currency(this.frm.doc, ["total_taxes_and_charges"]);
 
@@ -729,8 +744,10 @@ erpnext.taxes_and_totals = class TaxesAndTotals extends erpnext.payments {
 	}
 
 	get_total_for_discount_amount() {
-		if(this.frm.doc.apply_discount_on == "Net Total")
+		const doc = this.frm.doc;
-			return this.frm.doc.net_total;
+
+		if (doc.apply_discount_on == "Net Total" || !doc.taxes?.length)
+			return doc.net_total;
 
 		let total_actual_tax = 0.0;
 		let actual_taxes_dict = {};
@@ -745,7 +762,7 @@ erpnext.taxes_and_totals = class TaxesAndTotals extends erpnext.payments {
 			};
 		}
 
-		$.each(this.frm.doc["taxes"] || [], function(i, tax) {
+		doc.taxes.forEach(tax => {
 			if (["Actual", "On Item Quantity"].includes(tax.charge_type)) {
 				update_actual_taxes_dict(tax, tax.tax_amount);
 				return;
@@ -760,7 +777,7 @@ erpnext.taxes_and_totals = class TaxesAndTotals extends erpnext.payments {
 			update_actual_taxes_dict(tax, base_tax_amount * tax.rate / 100);
 		});
 
-		return this.frm.doc.grand_total - total_actual_tax;
+		return (this.grand_total_for_distributing_discount || doc.grand_total) - total_actual_tax;
 	}
 
 	calculate_total_advance(update_paid_amount) {