Client records have come in for the March 2022 year and client apparently was tempted by a good offer so sold electric car at the end of March, but didn't replace until May. Key member of staff left in January and client expected profits to be significantly affected in the final quarter to March 2022 so opted to reduce payments on account by £10K. In fact figures not too bad and with the unexpected balancing charge on the car it is clear that the payments on account should have been left as they were.
Client happy to pay now & aware of penalty, interest etc. Would it be best to file the current tax return now - which would need amending later to fine tune figures, or do I phone HMRC to advise situation or does client just pay the balance owing & estimate of interest & penalty & it will all be sorted when the return is finalised in a few weeks?