We have a few policies that was written before we were VAT registered. The commission on these policies are as and when. Meaning we get a small payout every month for a certain period.

Our VAT registration has now been processed and we need to declare VAT on commission earned. The problem is now that the provider doesn't want to pay us VAT on these existing policies as it was pre-vat. We however get this commission on a monthly basis and should probably pay VAT on them.

What can be done about this situation? Should be backdate all those payments to the months the policies were written so that effectively they are not included as income post-vat? Or is the provider in the wrong here?