diff --git a/erpnext/selling/doctype/sales_order/sales_order.py b/erpnext/selling/doctype/sales_order/sales_order.py
index 75260a5a3fa..0118e89cd3c 100755
--- a/erpnext/selling/doctype/sales_order/sales_order.py
+++ b/erpnext/selling/doctype/sales_order/sales_order.py
@@ -1144,6 +1144,17 @@ def make_sales_invoice(source_name, target_doc=None, ignore_permissions=False, a
 		target.debit_to = get_party_account("Customer", source.customer, source.company)
 
 	def update_item(source, target, source_parent):
+		def get_billed_qty(so_item_name):
+			from frappe.query_builder.functions import Sum
+
+			table = frappe.qb.DocType("Sales Invoice Item")
+			query = (
+				frappe.qb.from_(table)
+				.select(Sum(table.qty).as_("qty"))
+				.where((table.docstatus == 1) & (table.so_detail == so_item_name))
+			)
+			return query.run(pluck="qty")[0] or 0
+
 		if source_parent.has_unit_price_items:
 			# 0 Amount rows (as seen in Unit Price Items) should be mapped as it is
 			pending_amount = flt(source.amount) - flt(source.billed_amt)
@@ -1153,8 +1164,8 @@ def make_sales_invoice(source_name, target_doc=None, ignore_permissions=False, a
 
 		target.base_amount = target.amount * flt(source_parent.conversion_rate)
 		target.qty = (
-			target.amount / flt(source.rate)
-			if (source.rate and source.billed_amt)
+			source.qty - get_billed_qty(source.name)
+			if (source.qty and source.billed_amt)
 			else (source.qty if is_unit_price_row(source) else source.qty - source.returned_qty)
 		)
 
diff --git a/erpnext/selling/doctype/sales_order/test_sales_order.py b/erpnext/selling/doctype/sales_order/test_sales_order.py
index c5898a5ffaa..04a3a989cae 100644
--- a/erpnext/selling/doctype/sales_order/test_sales_order.py
+++ b/erpnext/selling/doctype/sales_order/test_sales_order.py
@@ -2396,6 +2396,30 @@ class TestSalesOrder(AccountsTestMixin, FrappeTestCase):
 		self.assertFalse(so.per_billed)
 		self.assertEqual(so.status, "To Deliver and Bill")
 
+	def test_pending_quantity_after_update_item_during_invoice_creation(self):
+		so = make_sales_order(qty=30, rate=100)
+
+		si1 = make_sales_invoice(so.name)
+		si1.get("items")[0].qty = 10
+		si1.insert()
+		si1.submit()
+
+		first_item_of_so = so.get("items")[0]
+		trans_item = json.dumps(
+			[
+				{
+					"item_code": first_item_of_so.item_code,
+					"rate": 1000,
+					"qty": first_item_of_so.qty,
+					"docname": first_item_of_so.name,
+				},
+			]
+		)
+		update_child_qty_rate("Sales Order", trans_item, so.name)
+
+		si2 = make_sales_invoice(so.name)
+		self.assertEqual(si2.items[0].qty, 20)
+
 
 def automatically_fetch_payment_terms(enable=1):
 	accounts_settings = frappe.get_doc("Accounts Settings")