The finance commission has been posted to a deal at the point of sale and a receipt post to confirm that this money has been received. The deal has been closed.
If for any reason the finance company decides to clawback the finance commission sometime later it should be dealt with within the accounts side of the system. The deal should never be reopened to deal with this.
The reason being is that at the time the deal was closed you did receive this money. So everything was correct and profit on the deal was correct. Money received has been allocated within the bank and reconciled.
Clawbacks are an expense to the sales department so should be dealt with within the purchase leader as an invoice and coding it to finance commission nominal code to reduce the value.