There may be times when you need to recalculate a VAT Return. For example, because you’ve added some extra transactions for that period but didn’t include them on the original return.
You can recalculate your VAT Return if:
You can't recalculate it if you’ve already submitted your return to HMRC or marked it as paid.
Instead, the next time you create a return, you’re asked if you want to include the transactions from a previous period. Select Yes, and they’re included on the return.
The VAT Return recalculates and you can then follow the steps to create and submit a VAT Return as normal.