Direct Answer
Match the Box 6 total (total value of sales) on your VAT return with the total credits in your bank statement, excluding VAT. Differences usually arise from VAT Cash Accounting scheme timings, zero-rated exports, or capital introduced.
The MTD Environment
Under Making Tax Digital (MTD), HMRC has greater visibility into your digital records. A bank statement that shows significantly higher cash inflows than what is declared in Box 6 of your VAT return can trigger a compliance check.
Cash vs. Accrual VAT Accounting
If you use the VAT Cash Accounting Scheme, your VAT return exactly follows your bank statement (you only pay VAT when your customer pays you). If you use standard (accrual) accounting, your VAT return is based on invoice dates. This timing difference is the most common reason bank credits don't match your quarterly VAT return.