fix: use correct exchange rate for multi-currency bank reconciliation payments (#59144)

* fix: use correct exchange rate for multi-currency bank reconciliation payments

* test: exchange rate for multi-currency bank reconciliation payment

(cherry picked from commit 04c949a662)

erpnext/accounts/doctype/bank_reconciliation_tool/bank_reconciliation_tool.py

@@ -796,6 +796,7 @@ def create_bulk_payment_entry_and_reconcile(
 				"deposit",
 				"withdrawal",
 				"bank_account",
+				"company",
 				"currency",
 				"unallocated_amount",
 				"date",
@@ -830,11 +831,7 @@ def create_bulk_payment_entry_and_reconcile(
 				"paid_from": paid_from,
 				"paid_to": paid_to,
 				"paid_amount": bank_transaction.unallocated_amount,
-				"base_paid_amount": bank_transaction.unallocated_amount,
 				"received_amount": bank_transaction.unallocated_amount,
-				"base_received_amount": bank_transaction.unallocated_amount,
-				"target_exchange_rate": 1,
-				"source_exchange_rate": 1,
 				"reference_date": bank_transaction.date,
 				"posting_date": bank_transaction.date,
 				"reference_no": (bank_transaction.reference_number or bank_transaction.description or "")[
@@ -843,6 +840,8 @@ def create_bulk_payment_entry_and_reconcile(
 			}
 		)
 
+		set_multi_currency_amounts(payment_entry_doc)
+
 		payment_entry_doc.insert()
 		payment_entry_doc.submit()
 
@@ -881,6 +880,7 @@ def create_payment_entry_and_reconcile(bank_transaction_name: str | int, payment
 			"doctype": "Payment Entry",
 		}
 	)
+	set_multi_currency_amounts(payment_entry)
 	payment_entry.insert()
 	payment_entry.submit()
 	transaction = reconcile_vouchers(
@@ -903,6 +903,33 @@ def create_payment_entry_and_reconcile(bank_transaction_name: str | int, payment
 	}
 
 
+def set_multi_currency_amounts(pe):
+	"""Set real exchange rates when the bank and party accounts differ in currency."""
+	company_currency = frappe.get_cached_value("Company", pe.company, "default_currency")
+	pe.paid_from_account_currency = frappe.get_cached_value("Account", pe.paid_from, "account_currency")
+	pe.paid_to_account_currency = frappe.get_cached_value("Account", pe.paid_to, "account_currency")
+
+	pe.source_exchange_rate = (
+		1.0
+		if pe.paid_from_account_currency == company_currency
+		else get_exchange_rate(pe.paid_from_account_currency, company_currency, pe.posting_date)
+	)
+	pe.target_exchange_rate = (
+		1.0
+		if pe.paid_to_account_currency == company_currency
+		else get_exchange_rate(pe.paid_to_account_currency, company_currency, pe.posting_date)
+	)
+
+	# derive the party-side amount from the authoritative bank-side amount; Payment Entry books any
+	# rounding residual to Exchange Gain/Loss during validation (set_exchange_gain_loss)
+	if pe.payment_type == "Receive" and pe.source_exchange_rate:
+		base_amount = flt(pe.received_amount) * pe.target_exchange_rate
+		pe.paid_amount = flt(base_amount / pe.source_exchange_rate, pe.precision("paid_amount"))
+	elif pe.payment_type == "Pay" and pe.target_exchange_rate:
+		base_amount = flt(pe.paid_amount) * pe.source_exchange_rate
+		pe.received_amount = flt(base_amount / pe.target_exchange_rate, pe.precision("received_amount"))
+
+
 @frappe.whitelist(methods=["GET"])
 def search_for_transfer_transaction(transaction_id: str | int):
 	"""

erpnext/accounts/doctype/bank_reconciliation_tool/test_bank_reconciliation_tool.py

@@ -2,12 +2,16 @@
 # See license.txt
 
 
+from unittest.mock import patch
+
 import frappe
 from frappe import qb
 from frappe.utils import add_days, today
 
 from erpnext.accounts.doctype.bank_reconciliation_tool.bank_reconciliation_tool import (
 	auto_reconcile_vouchers,
+	create_bulk_payment_entry_and_reconcile,
+	create_payment_entry_and_reconcile,
 	get_auto_reconcile_message,
 	get_bank_transactions,
 	get_linked_payments,
@@ -16,6 +20,8 @@ from erpnext.accounts.doctype.payment_entry.test_payment_entry import create_pay
 from erpnext.accounts.test.accounts_mixin import AccountsTestMixin
 from erpnext.tests.utils import ERPNextTestSuite
 
+RATE_METHOD = "erpnext.accounts.doctype.bank_reconciliation_tool.bank_reconciliation_tool.get_exchange_rate"
+
 
 class TestBankReconciliationTool(ERPNextTestSuite, AccountsTestMixin):
 	def setUp(self):
@@ -226,3 +232,117 @@ class TestBankReconciliationTool(ERPNextTestSuite, AccountsTestMixin):
 		self.assertIn("1 Transaction Partially Reconciled", singular)
 		plural, _ = get_auto_reconcile_message(["p1", "p2"], [])
 		self.assertIn("2 Transactions Partially Reconciled", plural)
+
+	def test_multi_currency_pay_converts_and_balances(self):
+		# withdrawal from an INR bank paying a USD supplier; rate 3.0 makes 100/3 non-exact
+		self.enable_multi_currency_setup()
+		pe = self.reconcile_new_payment(
+			self.make_multi_currency_txn(withdrawal=100),
+			payment_type="Pay",
+			party_type="Supplier",
+			party=self.supplier,
+			party_account=self.creditors_usd,
+			paid_from=self.bank,
+			paid_to=self.creditors_usd,
+			rate=3.0,
+		)
+		self.assertEqual(pe.docstatus, 1)  # submits despite the rounding residual
+		self.assertEqual((pe.source_exchange_rate, pe.target_exchange_rate), (1.0, 3.0))
+		self.assertEqual((pe.paid_amount, pe.received_amount), (100, 33.33))  # bank side kept, 100/3
+		self.assertEqual(pe.difference_amount, 0)
+		# Payment Entry auto-books the rounding residual to Exchange Gain/Loss
+		self.assertTrue(pe.deductions[0].is_exchange_gain_loss)
+		self.assertEqual(pe.deductions[0].amount, 0.01)  # 100 - 33.33 * 3
+
+	def test_multi_currency_receive_converts_and_balances(self):
+		# deposit into an INR bank from a USD customer; the party side must convert
+		self.enable_multi_currency_setup()
+		pe = self.reconcile_new_payment(
+			self.make_multi_currency_txn(deposit=100),
+			payment_type="Receive",
+			party_type="Customer",
+			party=self.customer,
+			party_account=self.debtors_usd,
+			paid_from=self.debtors_usd,
+			paid_to=self.bank,
+			rate=3.0,
+		)
+		self.assertEqual(pe.docstatus, 1)
+		self.assertEqual((pe.source_exchange_rate, pe.target_exchange_rate), (3.0, 1.0))
+		self.assertEqual((pe.received_amount, pe.paid_amount), (100, 33.33))  # bank side kept, 100/3
+		self.assertEqual(pe.difference_amount, 0)
+
+	def test_multi_currency_bulk_pay_converts_and_balances(self):
+		# the bulk path builds the Payment Entry itself, so it must convert too
+		self.enable_multi_currency_setup()
+		txn = self.make_multi_currency_txn(withdrawal=100)
+		with patch(RATE_METHOD, return_value=3.0):
+			result = create_bulk_payment_entry_and_reconcile(
+				[txn.name], "Supplier", self.supplier, self.creditors_usd
+			)
+
+		pe = frappe.get_doc("Payment Entry", result[0]["payment_entry"].name)
+		self.assertEqual(pe.docstatus, 1)
+		self.assertEqual(pe.target_exchange_rate, 3.0)
+		self.assertEqual((pe.paid_amount, pe.received_amount), (100, 33.33))
+		self.assertEqual(pe.difference_amount, 0)
+
+	def enable_multi_currency_setup(self):
+		# USD party/accounts + a company gain/loss account to absorb rounding residuals
+		self.company_abbr = "_TC"
+		self.create_supplier(supplier_name="_Test Supplier USD", currency="USD")
+		self.create_customer(customer_name="_Test Customer USD", currency="USD")
+		self.create_usd_payable_account()
+		self.create_usd_receivable_account()
+		self.set_party_account("Supplier", self.supplier, self.creditors_usd)
+		if not frappe.db.get_value("Company", self.company, "exchange_gain_loss_account"):
+			frappe.db.set_value(
+				"Company", self.company, "exchange_gain_loss_account", "Exchange Gain/Loss - _TC"
+			)
+
+	def set_party_account(self, party_type, party, account):
+		doc = frappe.get_doc(party_type, party)
+		if not any(row.company == self.company for row in doc.accounts):
+			doc.append("accounts", {"company": self.company, "account": account})
+			doc.save()
+
+	def make_multi_currency_txn(self, withdrawal=0, deposit=0):
+		return (
+			frappe.get_doc(
+				{
+					"doctype": "Bank Transaction",
+					"date": today(),
+					"withdrawal": withdrawal,
+					"deposit": deposit,
+					"bank_account": self.bank_account,
+					"currency": "INR",
+					"reference_number": "TEST-FX-REF",
+				}
+			)
+			.save()
+			.submit()
+		)
+
+	def reconcile_new_payment(
+		self, txn, *, payment_type, party_type, party, party_account, paid_from, paid_to, rate
+	):
+		# mimics the /banking frontend, which sends a hardcoded 1:1 rate
+		payment_entry_doc = {
+			"payment_type": payment_type,
+			"company": self.company,
+			"party_type": party_type,
+			"party": party,
+			"party_account": party_account,
+			"paid_from": paid_from,
+			"paid_to": paid_to,
+			"paid_amount": txn.unallocated_amount,
+			"received_amount": txn.unallocated_amount,
+			"source_exchange_rate": 1,
+			"target_exchange_rate": 1,
+			"posting_date": today(),
+			"reference_no": f"TEST-FX-{payment_type}",
+			"reference_date": today(),
+		}
+		with patch(RATE_METHOD, return_value=rate):
+			result = create_payment_entry_and_reconcile(txn.name, payment_entry_doc)
+		return frappe.get_doc("Payment Entry", result["payment_entry"].name)