fix: post customer withholding as a Deduct tax row, not a deduction

With a deduction row ERPNext treats Paid Amount as cash received and
credits the party for paid + deduction, so a gross Paid Amount (what Get
Outstanding Invoices fills) over-credited Debtors and posted the gross
to the bank. Use the taxes table with add_deduct_tax=Deduct like
supplier TDS: Paid Amount is the gross settlement, bank receives paid
minus withholding, receivable is debited. Override Payment Entry
build_gl_map to flag the bank entry post_net_value so the merged bank
line shows the net amount.

default_thai_company/hooks.py

@@ -145,6 +145,7 @@ fixtures = [
 
 override_doctype_class = {
 	"Sales Invoice": "default_thai_company.tax_withholding.ThaiSalesInvoice",
+	"Payment Entry": "default_thai_company.tax_withholding.ThaiPaymentEntry",
 }
 
 # Document Events

default_thai_company/tax_withholding.py

@@ -1,5 +1,6 @@
 import erpnext
 import frappe
+from erpnext.accounts.doctype.payment_entry.payment_entry import PaymentEntry
 from erpnext.accounts.doctype.sales_invoice.sales_invoice import SalesInvoice
 from erpnext.accounts.doctype.tax_withholding_category.tax_withholding_category import (
 	get_tax_withholding_details,
@@ -157,15 +158,31 @@ class ThaiSalesInvoice(SalesInvoice):
 			)
 
 
+class ThaiPaymentEntry(PaymentEntry):
+	def build_gl_map(self):
+		"""A "Deduct" tax row on a receipt posts bank Dr gross and bank Cr
+		withholding; ERPNext merges them into one entry but only nets it when
+		the bank entry itself carries `post_net_value`. Set it so the bank
+		ledger shows the amount that actually arrived."""
+		gl_entries = super().build_gl_map()
+		if self.payment_type == "Receive" and self.party_type == "Customer" and self.get("taxes"):
+			for entry in gl_entries:
+				if entry.account == self.paid_to:
+					entry.post_net_value = True
+		return gl_entries
+
+
 def set_customer_withholding(doc, method=None):
 	"""Payment Entry.validate: tax withheld by the customer on a Receive entry
-	becomes a deduction to the company's withholding receivable account.
+	is posted like ERPNext's supplier TDS, as a "Deduct" row in the taxes
+	table against the withholding receivable account.
 
-	Withholding is rate x pre-VAT amount of each allocated reference, prorated
+	`paid_amount` is the gross amount settled against the invoices (what
-	by the allocation. `paid_amount` is the cash actually received, so the
+	"Get Outstanding Invoices" fills in); the bank receives paid minus the
-	deduction closes the difference against the gross allocation. Runs after
+	withholding (`received_amount_after_tax`). Withholding is rate x pre-VAT
-	the controller's validate (exchange rates and allocations are final), then
+	amount of each allocated reference, prorated by the allocation. Runs after
-	re-derives the two amounts that depend on deductions.
+	the controller's validate, then re-runs the tax computation so the row's
+	base amounts and totals are final within this save.
 	"""
 	if doc.party_type != "Customer" or doc.payment_type != "Receive" or not doc.apply_tax_withholding_amount:
 		return
@@ -181,20 +198,22 @@ def set_customer_withholding(doc, method=None):
 		frappe.throw(_("Account {0} not found for Company {1}").format(ASSET_ACCOUNT, doc.company))
 
 	amount, description = get_customer_withholding(doc)
-	row = next((d for d in doc.deductions if d.account == account), None)
+	row = next((d for d in doc.taxes if d.account_head == account), None)
 
 	if not amount:
 		if row:
 			doc.remove(row)
 	else:
 		if not row:
-			row = doc.append("deductions", {"account": account})
+			row = doc.append(
-		row.amount = amount
+				"taxes", {"account_head": account, "charge_type": "Actual", "add_deduct_tax": "Deduct"}
+			)
+		row.tax_amount = amount
 		row.description = description
 		row.cost_center = doc.cost_center or erpnext.get_default_cost_center(doc.company)
 
-	doc.set_unallocated_amount()
+	doc.apply_taxes()
-	doc.set_difference_amount()
+	doc.set_amounts_after_tax()
 
 
 def get_customer_withholding(doc):

default_thai_company/tests/test_tax_withholding.py

@@ -71,7 +71,7 @@ class TestTaxWithholding(FrappeTestCase):
 			}
 		).insert()
 
-	def make_invoice(self, rate=10000, category=None):
+	def make_invoice(self, rate=10000, category=None, inclusive=False):
 		si = frappe.get_doc(
 			{
 				"doctype": "Sales Invoice",
@@ -87,6 +87,7 @@ class TestTaxWithholding(FrappeTestCase):
 						"account_head": self.vat.name,
 						"rate": 7,
 						"description": "VAT 7%",
+						"included_in_print_rate": int(inclusive),
 					}
 				],
 			}
@@ -94,7 +95,8 @@ class TestTaxWithholding(FrappeTestCase):
 		si.set_missing_values()
 		return si.submit()
 
-	def make_receipt(self, invoice, allocated, paid, apply=1):
+	def make_receipt(self, invoice, allocated, apply=1):
+		"""Paid amount is the gross allocation; withholding reduces what reaches the bank."""
 		return frappe.get_doc(
 			{
 				"doctype": "Payment Entry",
@@ -105,8 +107,8 @@ class TestTaxWithholding(FrappeTestCase):
 				"posting_date": nowdate(),
 				"paid_from": f"Debtors - {ABBR}",
 				"paid_to": f"Cash - {ABBR}",
-				"paid_amount": paid,
+				"paid_amount": allocated,
-				"received_amount": paid,
+				"received_amount": allocated,
 				"apply_tax_withholding_amount": apply,
 				"references": [
 					{
@@ -118,6 +120,9 @@ class TestTaxWithholding(FrappeTestCase):
 			}
 		).insert()
 
+	def withheld(self, pe):
+		return [(t.account_head, t.add_deduct_tax, t.tax_amount) for t in pe.taxes]
+
 	def category_account(self, category, company=COMPANY):
 		return frappe.db.get_value(
 			"Tax Withholding Account",
@@ -181,44 +186,55 @@ class TestTaxWithholding(FrappeTestCase):
 	def test_receipt_uses_invoice_category_over_customer_category(self):
 		si = self.make_invoice(category="WHT 5% - Rent")
 		self.assertEqual(si.withholding_tax_amount, 500.0)
-		pe = self.make_receipt(si, allocated=10700, paid=10200)
+		pe = self.make_receipt(si, allocated=10700)
-		self.assertEqual([(d.account, d.amount) for d in pe.deductions], [(self.receivable, 500.0)])
+		self.assertEqual(self.withheld(pe), [(self.receivable, "Deduct", 500.0)])
-		self.assertEqual(pe.difference_amount, 0)
+		self.assertEqual(pe.received_amount_after_tax, 10200.0)
 
 	def test_receipt_deducts_withholding_and_settles_invoice(self):
 		si = self.make_invoice()
-		pe = self.make_receipt(si, allocated=10700, paid=10400)
+		pe = self.make_receipt(si, allocated=10700)
 
 		self.assertEqual(pe.tax_withholding_category, "WHT 3% - Service")
-		self.assertEqual([(d.account, d.amount) for d in pe.deductions], [(self.receivable, 300.0)])
+		self.assertEqual(self.withheld(pe), [(self.receivable, "Deduct", 300.0)])
-		self.assertEqual(pe.difference_amount, 0)
+		self.assertEqual((pe.paid_amount, pe.received_amount_after_tax), (10700.0, 10400.0))
+		self.assertEqual((pe.unallocated_amount, pe.difference_amount), (0, 0))
 
 		pe.submit()
-		gl = {
+		gl = {}
-			g.account: (g.debit, g.credit)
 		for g in frappe.get_all(
 			"GL Entry", filters={"voucher_no": pe.name}, fields=["account", "debit", "credit"]
-			)
+		):
-		}
+			gl.setdefault(g.account, [0, 0])
-		self.assertEqual(gl[f"Cash - {ABBR}"], (10400.0, 0.0))
+			gl[g.account][0] += g.debit
-		self.assertEqual(gl[self.receivable], (300.0, 0.0))
+			gl[g.account][1] += g.credit
-		self.assertEqual(gl[f"Debtors - {ABBR}"], (0.0, 10700.0))
+		self.assertEqual(gl[f"Cash - {ABBR}"], [10400.0, 0.0])
+		self.assertEqual(gl[self.receivable], [300.0, 0.0])
+		self.assertEqual(gl[f"Debtors - {ABBR}"], [0.0, 10700.0])
+		self.assertEqual(len(gl), 3)
 		self.assertEqual(frappe.db.get_value("Sales Invoice", si.name, "outstanding_amount"), 0)
 
+	def test_inclusive_vat_invoice_withholds_on_pre_vat_amount(self):
+		si = self.make_invoice(inclusive=True)  # 10,000 incl. 7% VAT -> net 9,345.79
+		self.assertEqual((si.net_total, si.grand_total), (9345.79, 10000.0))
+		self.assertEqual(si.withholding_tax_amount, 280.37)
+		pe = self.make_receipt(si, allocated=10000)
+		self.assertEqual(self.withheld(pe), [(self.receivable, "Deduct", 280.37)])
+		self.assertEqual(pe.received_amount_after_tax, 9719.63)
+
 	def test_partial_allocation_prorates_withholding(self):
 		si = self.make_invoice()
-		pe = self.make_receipt(si, allocated=5350, paid=5200)
+		pe = self.make_receipt(si, allocated=5350)
-		self.assertEqual([(d.account, d.amount) for d in pe.deductions], [(self.receivable, 150.0)])
+		self.assertEqual(self.withheld(pe), [(self.receivable, "Deduct", 150.0)])
-		self.assertEqual(pe.difference_amount, 0)
+		self.assertEqual(pe.received_amount_after_tax, 5200.0)
 
 	def test_below_single_threshold_has_no_deduction(self):
 		si = self.make_invoice(rate=800)  # net 800 < 1,000 threshold
-		pe = self.make_receipt(si, allocated=856, paid=856)
+		pe = self.make_receipt(si, allocated=856)
-		self.assertEqual(pe.deductions, [])
+		self.assertEqual(pe.taxes, [])
-		self.assertEqual(pe.difference_amount, 0)
+		self.assertEqual(pe.received_amount_after_tax, 856.0)
 
 	def test_unchecked_receipt_is_untouched(self):
 		si = self.make_invoice()
-		pe = self.make_receipt(si, allocated=10700, paid=10700, apply=0)
+		pe = self.make_receipt(si, allocated=10700, apply=0)
-		self.assertEqual(pe.deductions, [])
+		self.assertEqual(pe.taxes, [])
-		self.assertEqual(pe.difference_amount, 0)
+		self.assertEqual(pe.received_amount_after_tax, 10700.0)