feat(accounts): split bank charges from exchange gain/loss on multi-currency transfers (#58071)

In a multi-currency Internal Transfer, the paid-vs-received difference was
booked entirely to Exchange Gain/Loss, so a bank charge entered as a deduction
pushed the Difference Amount non-zero and blocked submission. The exchange
gain/loss row now absorbs only the residual after user-entered deductions,
letting a Bank Charges row and the Exchange Gain/Loss row coexist and net to
zero.

erpnext/accounts/doctype/payment_entry/payment_entry.js

@@ -1279,8 +1279,14 @@ frappe.ui.form.on("Payment Entry", {
 		await frappe.after_ajax();
 		const base_paid_amount = frm.doc.base_paid_amount || 0;
 		const base_received_amount = frm.doc.base_received_amount || 0;
+		let other_deductions = 0;
+		if (frm.doc.payment_type === "Internal Transfer") {
+			other_deductions = (frm.doc.deductions || [])
+				.filter((row) => !row.is_exchange_gain_loss)
+				.reduce((sum, row) => sum + flt(row.amount), 0);
+		}
 		const exchange_gain_loss = flt(
-			base_paid_amount - base_received_amount,
+			base_paid_amount - base_received_amount - other_deductions,
 			get_deduction_amount_precision()
 		);
 
@@ -1857,11 +1863,19 @@ frappe.ui.form.on("Payment Entry Deduction", {
 	},
 
 	amount: function (frm) {
-		frm.events.set_unallocated_amount(frm);
+		if (frm.doc.payment_type === "Internal Transfer") {
+			frm.events.set_exchange_gain_loss_deduction(frm);
+		} else {
+			frm.events.set_unallocated_amount(frm);
+		}
 	},
 
 	deductions_remove: function (frm) {
-		frm.events.set_unallocated_amount(frm);
+		if (frm.doc.payment_type === "Internal Transfer") {
+			frm.events.set_exchange_gain_loss_deduction(frm);
+		} else {
+			frm.events.set_unallocated_amount(frm);
+		}
 	},
 });
 

erpnext/accounts/doctype/payment_entry/payment_entry.py

@@ -1118,8 +1118,14 @@ class PaymentEntry(AccountsController):
 			)
 
 	def set_exchange_gain_loss(self):
+		other_deductions = 0
+		if self.payment_type == "Internal Transfer":
+			other_deductions = sum(
+				flt(row.amount) for row in self.get("deductions") if not row.is_exchange_gain_loss
+			)
+
 		exchange_gain_loss = flt(
-			self.base_paid_amount - self.base_received_amount,
+			self.base_paid_amount - self.base_received_amount - other_deductions,
 			self.precision("amount", "deductions"),
 		)
 

erpnext/accounts/doctype/payment_entry/test_payment_entry.py

@@ -870,6 +870,64 @@ class TestPaymentEntry(ERPNextTestSuite):
 
 		self.validate_gl_entries(pe.name, expected_gle)
 
+	def test_cross_currency_transfer_splits_bank_charge_and_exchange_gain_loss(self):
+		exchange_gain_loss_account = frappe.db.get_value(
+			"Company", "_Test Company", "exchange_gain_loss_account"
+		)
+		bank_charges_account = create_account(
+			parent_account="Indirect Expenses - _TC",
+			account_name="_Test Bank Charges",
+			company="_Test Company",
+		)
+
+		pe = frappe.new_doc("Payment Entry")
+		pe.payment_type = "Internal Transfer"
+		pe.company = "_Test Company"
+		pe.paid_from = "_Test Bank USD - _TC"
+		pe.paid_to = "_Test Bank - _TC"
+		pe.paid_amount = 100
+		pe.source_exchange_rate = 50
+		pe.received_amount = 4500
+		pe.reference_no = "6"
+		pe.reference_date = nowdate()
+		pe.append(
+			"deductions",
+			{
+				"account": bank_charges_account,
+				"cost_center": "_Test Cost Center - _TC",
+				"amount": 100,
+			},
+		)
+
+		pe.setup_party_account_field()
+		pe.set_missing_values()
+		pe.set_exchange_rate()
+		pe.set_amounts()
+
+		deductions = {d.account: d for d in pe.deductions}
+		self.assertEqual(deductions[bank_charges_account].amount, 100)
+		self.assertEqual(deductions[exchange_gain_loss_account].amount, 400)
+		self.assertTrue(deductions[exchange_gain_loss_account].is_exchange_gain_loss)
+		self.assertEqual(pe.difference_amount, 0)
+
+		for d in pe.deductions:
+			d.cost_center = "_Test Cost Center - _TC"
+
+		pe.insert()
+		pe.submit()
+
+		expected_gle = dict(
+			(d[0], d)
+			for d in [
+				["_Test Bank USD - _TC", 0, 5000, None],
+				["_Test Bank - _TC", 4500, 0, None],
+				[exchange_gain_loss_account, 400.0, 0, None],
+				[bank_charges_account, 100.0, 0, None],
+			]
+		)
+
+		self.validate_gl_entries(pe.name, expected_gle)
+
 	def test_payment_against_negative_sales_invoice(self):
 		si1 = create_sales_invoice()