diff --git a/erpnext/selling/sales_common.js b/erpnext/selling/sales_common.js
index 12aca89..74b9bb9 100644
--- a/erpnext/selling/sales_common.js
+++ b/erpnext/selling/sales_common.js
@@ -403,15 +403,14 @@
 		// paid_amount and write_off_amount is only for POS Invoice
 		// total_advance is only for non POS Invoice
 		if(this.frm.doc.doctype == "Sales Invoice" && this.frm.doc.docstatus==0) {
-			if(this.frm.doc.paid_amount==null) {
-				frappe.model.round_floats_in(this.frm.doc, ["grand_total", "total_advance", "write_off_amount",
-					"paid_amount"]);
-				var total_amount_to_pay = this.frm.doc.grand_total - this.frm.doc.write_off_amount 
-					- this.frm.doc.total_advance;
-				this.frm.doc.paid_amount = this.frm.doc.is_pos ? flt (total_amount_to_pay) : 0.0;
-				this.frm.set_value("outstanding_amount", flt(total_amount_to_pay 
-					- this.frm.doc.paid_amount, precision("outstanding_amount")));
-			}
+			frappe.model.round_floats_in(this.frm.doc, ["grand_total", "total_advance", "write_off_amount",
+				"paid_amount"]);
+			var total_amount_to_pay = this.frm.doc.grand_total - this.frm.doc.write_off_amount 
+				- this.frm.doc.total_advance;
+			this.frm.doc.paid_amount = (this.frm.doc.is_pos && !this.frm.doc.paid_amount) ? 
+				flt(total_amount_to_pay): 0.0;
+			this.frm.set_value("outstanding_amount", flt(total_amount_to_pay 
+				- this.frm.doc.paid_amount, precision("outstanding_amount")));
 		}
 	},