I presume you are still trading with Supplier B. If that is the case, are they sending you regular statements?
Are these statements showing the overpayment on them? If not, why not? Could it be that they have already netted off the overpayment against later invoices? It should be obvious from the statements what has happened.
If you do not receive statements, then call the supplier and ask them for a full breakdown going as far back as 2021 and see what they have done with the overpayment.
If it is still sitting on their account, unmatched against invoices, then you can ask them either to: -
- send you a refund.
- set off against the next batch of invoices from the supplier.
Asking for a credit note will just cause confusion. How would they post the credit note -
Cr Supplier Account
Dr ??????????????????