Free tool
Does your VAT return add up?
Sense checks only, based on HMRC VAT Notice 700/12. Nothing you type leaves your browser.
Errors good software catches
- Arithmetic: Box 3 must equal Box 1 plus Box 2, and Box 5 must be the difference between Box 3 and Box 4.
- Format: Boxes 6 to 9 must be whole pounds. Box 5 can never be negative.
- Retyping errors: uploading a file from your records avoids transposed or missed digits.
- Wrong period: showing your open periods from HMRC stops you filing the wrong one.
Errors only your records can prevent
- Missing sales or purchase invoices.
- The wrong VAT rate on a sale.
- Reclaiming VAT without a valid VAT invoice, or on costs you cannot reclaim, such as business entertainment.
- Including transactions from outside the VAT period.
- Leaving zero-rated or exempt sales out of Box 6.
Sense checks for any VAT return
| Check | Why |
|---|---|
| Box 1 is no more than 20% of Box 6 | Output VAT above the standard rate on your sales usually means a mistake |
| Box 4 is no more than 20% of Box 7 | Reclaimed VAT above 20% of your purchases usually means a mistake |
| Box 4 has a value only if Box 7 does | VAT reclaimed with no purchases recorded does not add up |
| Similar to the same period last year | A big change you cannot explain is worth checking before you file |
If you find an error after filing
A submitted return cannot be changed. Correct net errors up to £10,000, or up to 1% of Box 6 with a £50,000 limit, on your next return, and report larger errors to HMRC.
How Swift VAT Pro checks your return
Swift VAT Pro takes your nine box totals from a CSV saved from your spreadsheet, works out Box 3 and Box 5, rounds pence in Boxes 6 to 9 with a note, checks every box against HMRC's limits and explains any HMRC error in plain English.
Every box checked before it goes to HMRC, from £5 a month
Swift VAT Pro works out Box 3 and Box 5, rounds pence in Boxes 6 to 9 with a note, and explains HMRC errors in plain English.
- Connect to HMRC on HMRC's own page with your Government Gateway sign-in. We never see that password.
- See your VAT periods, due dates, amounts owed and payments, read from HMRC.
- Upload your nine box totals as a CSV. Box 3 and Box 5 are worked out and every box is checked.
- Submit and keep HMRC's receipt. Reminder emails arrive before each due date.
No card needed · From £5 a month · Plans for up to 100 businesses · Filing through HMRC's MTD service since 2019
Final thoughts
Accurate VAT returns come from good records plus good checks. Keep figures moving digitally, let software catch the arithmetic, and sense-check the totals yourself before you submit.
Disclaimer: This guide gives general information, not advice for your business. If you are unsure how the rules apply to you, speak to an accountant or contact HMRC.
Frequently asked questions
Checked against HMRC VAT Notice 700/12, VAT Notice 700/45 and Swift VAT Pro's validation rules. November 2026.
How does software make VAT returns more accurate?
What VAT return errors does software not catch?
Should Box 1 be 20% of Box 6?
Can I change a VAT return after submitting it?
Why must Boxes 6 to 9 be whole pounds?
Every box checked before it goes to HMRC, from £5 a month.
Swift VAT Pro files your return to HMRC from the spreadsheet you already keep. From £5 a month.
No card needed · 2,900+ VAT returns filed since 2019