fix: check if tds deducted based on Purchase Taxes and Charges (#45161)

(cherry picked from commit 37a5767be5)

erpnext/accounts/doctype/tax_withholding_category/tax_withholding_category.py

@@ -270,6 +270,10 @@ def get_tax_amount(party_type, parties, inv, tax_details, posting_date, pan_no=N
 	tax_amount = 0
 
 	if party_type == "Supplier":
+		# if tds account is changed.
+		if not tax_deducted:
+			tax_deducted = is_tax_deducted_on_the_basis_of_inv(vouchers)
+
 		ldc = get_lower_deduction_certificate(inv.company, posting_date, tax_details, pan_no)
 		if tax_deducted:
 			net_total = inv.tax_withholding_net_total
@@ -304,6 +308,18 @@ def get_tax_amount(party_type, parties, inv, tax_details, posting_date, pan_no=N
 	return tax_amount, tax_deducted, tax_deducted_on_advances, voucher_wise_amount
 
 
+def is_tax_deducted_on_the_basis_of_inv(vouchers):
+	return frappe.db.exists(
+		"Purchase Taxes and Charges",
+		{
+			"parent": ["in", vouchers],
+			"is_tax_withholding_account": 1,
+			"parenttype": "Purchase Invoice",
+			"base_tax_amount_after_discount_amount": [">", 0],
+		},
+	)
+
+
 def get_invoice_vouchers(parties, tax_details, company, party_type="Supplier"):
 	doctype = "Purchase Invoice" if party_type == "Supplier" else "Sales Invoice"
 	field = (

erpnext/accounts/doctype/tax_withholding_category/test_tax_withholding_category.py

@@ -61,6 +61,49 @@ class TestTaxWithholdingCategory(FrappeTestCase):
 		for d in reversed(invoices):
 			d.cancel()
 
+	def test_tds_with_account_changed(self):
+		frappe.db.set_value(
+			"Supplier", "Test TDS Supplier", "tax_withholding_category", "Multi Account TDS Category"
+		)
+		invoices = []
+
+		# create invoices for lower than single threshold tax rate
+		for _ in range(2):
+			pi = create_purchase_invoice(supplier="Test TDS Supplier")
+			pi.submit()
+			invoices.append(pi)
+
+		# create another invoice whose total when added to previously created invoice,
+		# surpasses cumulative threshhold
+		pi = create_purchase_invoice(supplier="Test TDS Supplier")
+		pi.submit()
+
+		# assert equal tax deduction on total invoice amount until now
+		self.assertEqual(pi.taxes_and_charges_deducted, 3000)
+		self.assertEqual(pi.grand_total, 7000)
+		invoices.append(pi)
+
+		# account changed
+
+		frappe.db.set_value(
+			"Tax Withholding Account",
+			{"parent": "Multi Account TDS Category"},
+			"account",
+			"_Test Account VAT - _TC",
+		)
+
+		# TDS should be on invoice only even though account is changed
+		pi = create_purchase_invoice(supplier="Test TDS Supplier", rate=5000)
+		pi.submit()
+
+		# assert equal tax deduction on total invoice amount until now
+		self.assertEqual(pi.taxes_and_charges_deducted, 500)
+		invoices.append(pi)
+
+		# delete invoices to avoid clashing
+		for d in reversed(invoices):
+			d.cancel()
+
 	def test_single_threshold_tds(self):
 		invoices = []
 		frappe.db.set_value(
@@ -1063,6 +1106,16 @@ def create_tax_withholding_category_records():
 		consider_party_ledger_amount=1,
 	)
 
+	create_tax_withholding_category(
+		category_name="Multi Account TDS Category",
+		rate=10,
+		from_date=from_date,
+		to_date=to_date,
+		account="TDS - _TC",
+		single_threshold=0,
+		cumulative_threshold=30000,
+	)
+
 
 def create_tax_withholding_category(
 	category_name,