diff --git a/erpnext/accounts/doctype/payment_request/payment_request.py b/erpnext/accounts/doctype/payment_request/payment_request.py
index fc837c7..52eb29b 100644
--- a/erpnext/accounts/doctype/payment_request/payment_request.py
+++ b/erpnext/accounts/doctype/payment_request/payment_request.py
@@ -45,21 +45,20 @@
 			frappe.throw(_("To create a Payment Request reference document is required"))
 
 	def validate_payment_request_amount(self):
-		existing_payment_request_amount = get_existing_payment_request_amount(
-			self.reference_doctype, self.reference_name
+		existing_payment_request_amount = flt(
+			get_existing_payment_request_amount(self.reference_doctype, self.reference_name)
 		)
 
-		if existing_payment_request_amount:
-			ref_doc = frappe.get_doc(self.reference_doctype, self.reference_name)
-			if not hasattr(ref_doc, "order_type") or getattr(ref_doc, "order_type") != "Shopping Cart":
-				ref_amount = get_amount(ref_doc, self.payment_account)
+		ref_doc = frappe.get_doc(self.reference_doctype, self.reference_name)
+		if not hasattr(ref_doc, "order_type") or getattr(ref_doc, "order_type") != "Shopping Cart":
+			ref_amount = get_amount(ref_doc, self.payment_account)
 
-				if existing_payment_request_amount + flt(self.grand_total) > ref_amount:
-					frappe.throw(
-						_("Total Payment Request amount cannot be greater than {0} amount").format(
-							self.reference_doctype
-						)
+			if existing_payment_request_amount + flt(self.grand_total) > ref_amount:
+				frappe.throw(
+					_("Total Payment Request amount cannot be greater than {0} amount").format(
+						self.reference_doctype
 					)
+				)
 
 	def validate_currency(self):
 		ref_doc = frappe.get_doc(self.reference_doctype, self.reference_name)