Before you accept any invoice, you need to first make sure that it is valid. Let us examine the situations where an invoice should not be accepted.
Check if the invoice corresponds to an existing order (which is the case most of the time). If so, the invoice needs to include the purchase order number. Also, make sure that the PO number is correct.
Examine the item list. Make sure that all items are correct, not repeated, and are not in other invoices received earlier.
For each item, make sure that all details are correct.
If applicable, make sure that the shipment code exists and that it is correct.
If you are paying through wire transfers, then the bank details should be on the invoice. This is especially important in case something goes wrong while transferring the funds. Do not rely on bank details from older invoices.
If you are paying by cheque, make sure that the payee details are on the invoice.
Check that all VAT related values are correct. Refer to the VAT certificate that was provided by the supplier.
Check totals and calculations on the invoice. Do not trust the vendor on this, they could unwillingly make mistakes.
Every invoice needs to have a unique number. Make sure that the invoice number is valid and that it hasn’t been used before for that particular vendor or supplier.
Check the invoice date.
You have the right to reject an invoice if it is not due. See to PO, read the terms and conditions section.
Check that the work has been completed according to the scope. See project sign-off letter.
Check that all items are in the project scope. You don’t have to pay for anything not in the scope.
Check that the received goods or services are in line with the specifications.
Reject the invoice if the quality standards have not been met.
Make sure that items in the list are not in any other invoice.
If the invoice is not electronic, it must have a stamp and a signature to indicate that it has been officially authorized by the other side.