diff --git a/erpnext/accounts/doctype/tax_withholding_category/tax_withholding_category.py b/erpnext/accounts/doctype/tax_withholding_category/tax_withholding_category.py
index dd8caa60d7d..f6ce7739acd 100644
--- a/erpnext/accounts/doctype/tax_withholding_category/tax_withholding_category.py
+++ b/erpnext/accounts/doctype/tax_withholding_category/tax_withholding_category.py
@@ -7,7 +7,7 @@ import frappe
 from frappe import _
 from frappe.model.document import Document
 from frappe.query_builder.functions import Sum
-from frappe.utils import getdate
+from frappe.utils import cstr, getdate
 
 from erpnext import allow_regional
 from erpnext.controllers.accounts_controller import validate_account_head
@@ -48,7 +48,7 @@ class TaxWithholdingCategory(Document):
 		for d in self.get("rates"):
 			if getdate(d.from_date) >= getdate(d.to_date):
 				frappe.throw(_("Row #{0}: From Date cannot be before To Date").format(d.idx))
-			group_rates[d.tax_withholding_group].append(d)
+			group_rates[cstr(d.tax_withholding_group)].append(d)
 
 		# Validate overlapping dates within each group
 		for group, rates in group_rates.items():
@@ -92,10 +92,9 @@ class TaxWithholdingCategory(Document):
 
 	def get_applicable_tax_row(self, posting_date, tax_withholding_group):
 		for row in self.rates:
-			if (
-				getdate(row.from_date) <= getdate(posting_date) <= getdate(row.to_date)
-				and row.tax_withholding_group == tax_withholding_group
-			):
+			if getdate(row.from_date) <= getdate(posting_date) <= getdate(row.to_date) and cstr(
+				row.tax_withholding_group
+			) == cstr(tax_withholding_group):
 				return row
 
 		frappe.throw(_("No Tax Withholding data found for the current posting date."))
@@ -116,7 +115,7 @@ class TaxWithholdingDetails:
 	def __init__(
 		self,
 		tax_withholding_categories: list[str],
-		tax_withholding_group: str,
+		tax_withholding_group: str | None,
 		posting_date: str,
 		party_type: str,
 		party: str,
diff --git a/erpnext/accounts/doctype/tax_withholding_category/test_tax_withholding_category.py b/erpnext/accounts/doctype/tax_withholding_category/test_tax_withholding_category.py
index 13697084cbf..40de1933a34 100644
--- a/erpnext/accounts/doctype/tax_withholding_category/test_tax_withholding_category.py
+++ b/erpnext/accounts/doctype/tax_withholding_category/test_tax_withholding_category.py
@@ -999,6 +999,47 @@ class TestTaxWithholdingCategory(ERPNextTestSuite):
 
 		self.cleanup_invoices(invoices)
 
+	def test_null_and_empty_tax_withholding_group_are_equivalent(self):
+		"""
+		NULL and empty-string `tax_withholding_group` must be treated as the
+		same value.
+		"""
+		category = frappe.get_doc("Tax Withholding Category", "Cumulative Threshold TDS")
+		original_row = category.rates[0]
+		original_row.tax_withholding_group = None
+
+		# Part 1: validate_dates must detect overlap between NULL-group and
+		# empty-string-group rows covering the same date range.
+		category.append(
+			"rates",
+			{
+				"from_date": original_row.from_date,
+				"to_date": original_row.to_date,
+				"tax_withholding_group": "",
+				"tax_withholding_rate": original_row.tax_withholding_rate,
+			},
+		)
+		with self.assertRaises(frappe.ValidationError):
+			category.validate_dates()
+		category.rates.pop()
+
+		# Part 2: get_applicable_tax_row must match NULL <-> "" in either direction.
+		posting_date = original_row.from_date
+
+		row = category.get_applicable_tax_row(posting_date=posting_date, tax_withholding_group="")
+		self.assertEqual(row.name, original_row.name)
+
+		row = category.get_applicable_tax_row(posting_date=posting_date, tax_withholding_group=None)
+		self.assertEqual(row.name, original_row.name)
+
+		original_row.tax_withholding_group = ""
+		row = category.get_applicable_tax_row(posting_date=posting_date, tax_withholding_group=None)
+		self.assertEqual(row.name, original_row.name)
+
+		original_row.tax_withholding_group = None
+		with self.assertRaises(frappe.ValidationError):
+			category.get_applicable_tax_row(posting_date=posting_date, tax_withholding_group="194R")
+
 	def test_tds_calculation_on_net_total(self):
 		self.setup_party_with_category("Supplier", "Test TDS Supplier4", "Cumulative Threshold TDS")
 		invoices = []