VAT accounting is the part of bookkeeping that decides whether the return is a total or a reconstruction. Done as you go, every sale and purchase is split into net and VAT at the moment it is recorded, and the return is the sum of those splits. Done at the end, it is an archaeology exercise on a pile of receipts, and that is where both the errors and the missed input tax come from.
Split at the point of entry, not at the quarter end
Each transaction carries three facts: the net, the rate and the VAT. Record all three when the transaction is entered and the return becomes addition. The single most common error is treating a VAT-inclusive figure as if it were net, which overstates both the net and the VAT: at the standard rate the VAT is a sixth of the gross, not a fifth of it. The second most common is recording a purchase you cannot reclaim on, usually because there is no valid VAT invoice behind it.
The reconciliation that proves the return
A VAT reconciliation ties the VAT control account in your books to the boxes on the return. Output tax posted through the quarter should equal box 1; input tax posted should equal box 4; the balance carried should equal box 5. Where they differ the cause is nearly always one of three things: a transaction dated outside the period, a rate applied inconsistently between the invoice and the ledger, or a credit note posted without its VAT. Finding it before submission is a correction; finding it after is an amendment.
A checklist worth running before you submit
Does every sale in the period have a rate against it, and is any zero-rated or exempt line deliberate rather than blank? Does every purchase in box 4 have a valid VAT invoice showing the supplier's nine-digit number? Are credit notes in, with their VAT? Are personal or non-business proportions excluded? Does the control account tie to boxes 1, 4 and 5? Are the records in a digital form with digital links to whatever submits them? Those six questions catch most of what a first review would.
Questions people ask about vat accounting
What is a VAT reconciliation?
Tying the VAT control account in your books to the return: output tax to box 1, input tax to box 4, and the balance to box 5. A difference points at a dating, rate or credit-note problem.
Do I need a valid VAT invoice for every reclaim?
Yes, in the ordinary case. Without an invoice showing the supplier's VAT registration number, the date, the supply, the rate and the VAT, there is nothing supporting the box 4 entry.
What if I find an error after submitting?
Correct it. Small errors are normally adjusted on the next return and larger ones notified separately. Either way HMRC can charge a penalty for an inaccurate return, so a correction found and made is the cheaper outcome.