diff --git a/erpnext/accounts/report/sales_register/sales_register.py b/erpnext/accounts/report/sales_register/sales_register.py
index e711ec299a3..f76bbc6c6ef 100644
--- a/erpnext/accounts/report/sales_register/sales_register.py
+++ b/erpnext/accounts/report/sales_register/sales_register.py
@@ -347,14 +347,17 @@ def get_account_columns(invoice_list, include_payments):
 
 	if invoice_list:
 		# frappe drops ORDER BY for distinct queries on postgres (db_query), so sort in python to keep
-		# the generated account-column order deterministic and identical on both backends.
+		# the generated account-column order deterministic and identical on both backends. casefold
+		# reproduces MariaDB's case-insensitive collation order (the original raw SQL ORDER BY); plain
+		# sorted() would be case-sensitive and reorder columns vs the pre-effort MariaDB output.
 		income_accounts = sorted(
 			frappe.get_all(
 				"Sales Invoice Item",
 				filters={"docstatus": 1, "parent": ["in", [inv.name for inv in invoice_list]]},
 				pluck="income_account",
 				distinct=True,
-			)
+			),
+			key=str.casefold,
 		)
 
 		sales_taxes_query = get_taxes_query(invoice_list, "Sales Taxes and Charges", "Sales Invoice")
@@ -377,7 +380,8 @@ def get_account_columns(invoice_list, include_payments):
 				},
 				pluck="unrealized_profit_loss_account",
 				distinct=True,
-			)
+			),
+			key=str.casefold,
 		)
 
 	for account in income_accounts:
diff --git a/erpnext/accounts/report/sales_register/test_sales_register.py b/erpnext/accounts/report/sales_register/test_sales_register.py
index 132b7a0ee3b..f3ed2641633 100644
--- a/erpnext/accounts/report/sales_register/test_sales_register.py
+++ b/erpnext/accounts/report/sales_register/test_sales_register.py
@@ -55,6 +55,39 @@ class TestItemWiseSalesRegister(ERPNextTestSuite, AccountsTestMixin):
 			si = si.submit()
 		return si
 
+	def _ensure_income_account(self, account_name):
+		name = f"{account_name} - _TC"
+		if not frappe.db.exists("Account", name):
+			frappe.get_doc(
+				{
+					"doctype": "Account",
+					"account_name": account_name,
+					"parent_account": "Income - _TC",
+					"company": self.company,
+					"root_type": "Income",
+					"report_type": "Profit and Loss",
+					"account_type": "Income Account",
+				}
+			).insert()
+		return name
+
+	def test_income_account_columns_sorted_case_insensitively(self):
+		# The dynamic income-account columns must follow MariaDB's case-insensitive collation order and
+		# be identical on both engines. Plain python sorted() is case-sensitive (ASCII), so "ZZZ" would
+		# sort before "aaa"; casefold restores the pre-effort MariaDB order on both backends.
+		lower = self._ensure_income_account("aaa Test Income")
+		upper = self._ensure_income_account("ZZZ Test Income")
+		for account in (upper, lower):  # submit in non-casefold order
+			si = self.create_sales_invoice(do_not_submit=True)
+			si.items[0].income_account = account
+			si.submit()
+
+		filters = frappe._dict({"from_date": today(), "to_date": today(), "company": self.company})
+		columns = execute(filters)[0]
+		labels = [col["label"] for col in columns if col.get("label") in (lower, upper)]
+
+		self.assertEqual(labels, sorted([lower, upper], key=str.casefold))
+
 	def test_basic_report_output(self):
 		si = self.create_sales_invoice(rate=98)