diff --git a/erpnext/accounts/doctype/payment_request/payment_request.py b/erpnext/accounts/doctype/payment_request/payment_request.py
index 2f43914..7005c17 100644
--- a/erpnext/accounts/doctype/payment_request/payment_request.py
+++ b/erpnext/accounts/doctype/payment_request/payment_request.py
@@ -495,26 +495,22 @@
 	"""get amount based on doctype"""
 	dt = ref_doc.doctype
 	if dt in ["Sales Order", "Purchase Order"]:
-		grand_total = flt(ref_doc.rounded_total) - flt(ref_doc.advance_paid)
-
+		grand_total = flt(ref_doc.rounded_total) or flt(ref_doc.grand_total)
 	elif dt in ["Sales Invoice", "Purchase Invoice"]:
 		if ref_doc.party_account_currency == ref_doc.currency:
 			grand_total = flt(ref_doc.outstanding_amount)
 		else:
 			grand_total = flt(ref_doc.outstanding_amount) / ref_doc.conversion_rate
-
 	elif dt == "POS Invoice":
 		for pay in ref_doc.payments:
 			if pay.type == "Phone" and pay.account == payment_account:
 				grand_total = pay.amount
 				break
-
 	elif dt == "Fees":
 		grand_total = ref_doc.outstanding_amount
 
 	if grand_total > 0:
 		return grand_total
-
 	else:
 		frappe.throw(_("Payment Entry is already created"))
 
diff --git a/erpnext/accounts/doctype/payment_request/test_payment_request.py b/erpnext/accounts/doctype/payment_request/test_payment_request.py
index 477c726..4279aa4 100644
--- a/erpnext/accounts/doctype/payment_request/test_payment_request.py
+++ b/erpnext/accounts/doctype/payment_request/test_payment_request.py
@@ -45,7 +45,10 @@
 				frappe.get_doc(method).insert(ignore_permissions=True)
 
 	def test_payment_request_linkings(self):
-		so_inr = make_sales_order(currency="INR")
+		so_inr = make_sales_order(currency="INR", do_not_save=True)
+		so_inr.disable_rounded_total = 1
+		so_inr.save()
+
 		pr = make_payment_request(
 			dt="Sales Order",
 			dn=so_inr.name,