diff --git a/erpnext/selling/doctype/sales_order/sales_order.py b/erpnext/selling/doctype/sales_order/sales_order.py
index b6891930e42..f18b8762c7f 100755
--- a/erpnext/selling/doctype/sales_order/sales_order.py
+++ b/erpnext/selling/doctype/sales_order/sales_order.py
@@ -1176,6 +1176,17 @@ 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)
@@ -1185,8 +1196,8 @@ 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)
 		)