Keep source documents and explanations
Collect sales invoices, purchase invoices, relevant adjustments, payment evidence and your VAT account. Keep records of how unusual transactions were treated. HMRC generally requires VAT business records to be kept for at least six years, with exceptions and additional rules for some circumstances.
Use consistent references
Give each source document a stable reference that also appears in the ledger. Keep the original document, not just a calculator screenshot. A screenshot can support a check, but it does not establish who supplied what, the date of supply or the entitlement to input VAT.
Create a period-end folder
Store the reconciled totals, unresolved-item log, review notes and submission confirmation together. Keep adjustments traceable to their source and explain why they were made. Make sure backups can actually be restored and that access is available to the people responsible for the return.
Monthly maintenance beats a last-minute search
Resolve missing invoices and inconsistent tax codes while the transactions are recent. Reconcile bank allocations where relevant to your accounting method. Before disposing of old records, check the HMRC retention rules and any ongoing enquiry or other obligation.
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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.