Build a 12-month window
Create a worksheet with a row for each month and a taxable turnover column. Total the latest 12 rows. At the next review, add the new month and remove the oldest. Keep earlier versions so that you can see when a changing total first raised a question.
Separate calculation from classification
Reconcile your sales records before deciding what belongs in taxable turnover. Keep separate notes for exempt, outside-scope and unusual transactions. A bookkeeping total called revenue is not automatically the correct VAT registration figure.
Run a forward view too
A rolling total only looks backward. Add a review of upcoming contracts and expected taxable sales for the next 30 days alone. The two tests can produce different registration timing. Do not wait for the next annual accounts exercise to investigate a large new contract.
Save an evidence trail
Record the review date, person checking it, source ledger totals and unresolved items. Assign each question an owner and a follow-up date. When the total approaches a boundary, arrange a review of pricing and registration steps rather than making an unsupported assumption from the colour of a progress bar.
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Official sources
Sources checked: 2026-09-26. Check the official guidance for later changes.
Educational information and estimates. These tools do not submit VAT returns or determine the treatment of a specific transaction.