diff --git a/erpnext/accounts/doctype/payment_entry/payment_entry.js b/erpnext/accounts/doctype/payment_entry/payment_entry.js
index d96bc27..3be3925 100644
--- a/erpnext/accounts/doctype/payment_entry/payment_entry.js
+++ b/erpnext/accounts/doctype/payment_entry/payment_entry.js
@@ -872,7 +872,7 @@
 				&& frm.doc.base_total_allocated_amount < frm.doc.base_received_amount + total_deductions
 				&& frm.doc.total_allocated_amount < frm.doc.paid_amount + (total_deductions / frm.doc.source_exchange_rate)) {
 					unallocated_amount = (frm.doc.base_received_amount + total_deductions + frm.doc.base_total_taxes_and_charges
-						+ frm.doc.base_total_allocated_amount) / frm.doc.source_exchange_rate;
+						- frm.doc.base_total_allocated_amount) / frm.doc.source_exchange_rate;
 			} else if (frm.doc.payment_type == "Pay"
 				&& frm.doc.base_total_allocated_amount < frm.doc.base_paid_amount - total_deductions
 				&& frm.doc.total_allocated_amount < frm.doc.received_amount + (total_deductions / frm.doc.target_exchange_rate)) {