diff --git a/erpnext/accounts/doctype/payment_request/payment_request.py b/erpnext/accounts/doctype/payment_request/payment_request.py
index ae974a8cf0e..aaae8204a9b 100644
--- a/erpnext/accounts/doctype/payment_request/payment_request.py
+++ b/erpnext/accounts/doctype/payment_request/payment_request.py
@@ -667,11 +667,9 @@ def get_amount(ref_doc, payment_account=None):
 	elif dt in ["Sales Invoice", "Purchase Invoice"]:
 		if not ref_doc.get("is_pos"):
 			if ref_doc.party_account_currency == ref_doc.currency:
-				grand_total = flt(ref_doc.rounded_total or ref_doc.grand_total)
+				grand_total = flt(ref_doc.outstanding_amount)
 			else:
-				grand_total = flt(
-					flt(ref_doc.base_rounded_total or ref_doc.base_grand_total) / ref_doc.conversion_rate
-				)
+				grand_total = flt(flt(ref_doc.outstanding_amount) / ref_doc.conversion_rate)
 		elif dt == "Sales Invoice":
 			for pay in ref_doc.payments:
 				if pay.type == "Phone" and pay.account == payment_account: