It is very important when using cash accounting that VAT
periods are understood to make sure you close your VAT periods
before including transactions that should be on the next VAT
return.
With the cash accounting method, any
transaction that is 'allocated' or 'unallocated' on a customer or
supplier ledger will be included on the VAT return for the current
period - regardless of the date of the transaction.
You must close your VAT period on the last day
of your VAT period (or after the last payment/receipt has been
entered for that period) before any payments/receipts that should
appear in the next VAT return are entered.
If you do not close your VAT period
immediately, your VAT return will include payments/receipts dated
after the last day of the current VAT period.