diff --git a/erpnext/public/js/controllers/taxes_and_totals.js b/erpnext/public/js/controllers/taxes_and_totals.js
index bd5a136..3099184 100644
--- a/erpnext/public/js/controllers/taxes_and_totals.js
+++ b/erpnext/public/js/controllers/taxes_and_totals.js
@@ -22,7 +22,7 @@
 
 		item_rate = flt(item.rate_with_margin , precision("rate", item));
 
-		if (item.discount_percentage) {
+		if (item.discount_percentage && !item.discount_amount) {
 			item.discount_amount = flt(item.rate_with_margin) * flt(item.discount_percentage) / 100;
 		}