How to Correct a VAT Error: The Two Thresholds That Decide Your Route

Two numbers decide your route. Work out the net value of your VAT errors — everything you owe HMRC, minus everything HMRC owes you. If that net figure is £10,000 or less, you can put it right on your next VAT Return and move on. If it lands between £10,000 and £50,000, you can still correct it on the return, but only if it comes to 1% or less of the box 6 (net outputs) figure on the return for the period in which you discovered the errors. Bigger than £50,000, or over that 1% line, and you have to notify HMRC separately. And if the error was deliberate, none of those thresholds help you: it must be notified separately whatever it is worth.

Step one: work out the net error, not the biggest error

Most people get the route wrong because they look at the scariest single mistake instead of the arithmetic HMRC actually asks for. VAT Notice 700/45 tells you to work out two totals for the errors you have found on previous returns: the total amount due to HMRC, and the total amount due to you. The difference between those two is your net error, and that single figure is what the thresholds are measured against.

So a quarter where you under-declared £9,000 of output tax and separately failed to claim £4,000 of input tax does not give you a £9,000 error. It gives you a net error of £5,000. That works in your favour. It also works the other way, which is where people come unstuck. Once you have the net figure, the routing is mechanical.

If you want to sanity-check the return you are about to file the adjustment on, run the figures through our VAT Return calculator first. The routing decision depends on box 6, so it is worth having that number in front of you rather than in your head.

Route 1: correct it on your next VAT Return

This is the housekeeping route, and it is genuinely light-touch. HMRC's wording is that you adjust your VAT account if you have accounted for too much or too little tax, and include the value of that adjustment on your current VAT Return. There is no form, no letter and no waiting.

What you must not do is treat it as invisible. Keep a clear record of what the error was, which period it belonged to, whether it was input tax or output tax, and how you arrived at the adjustment figure. If HMRC opens a compliance check later, that record is the difference between an error that was handled properly and an error that looks like it was buried.

Worked example — Dawid, plumbing and heating contractor. Dawid is reviewing his last four quarters before his accountant closes the year. He finds three problems: £7,900 of output tax under-declared on commercial jobs where he applied the wrong rate, £1,500 of output tax under-declared on a deposit he treated as outside the scope, and £3,100 of input tax he never claimed on a van service plan. Total due to HMRC: £9,400. Total due to Dawid: £3,100. Net error: £6,300. That is under £10,000, none of it was deliberate, so Dawid adjusts his VAT account and puts £6,300 on his current return. He writes a one-page note for the file explaining each of the three errors and files it with the working papers.

Route 2: notify HMRC separately — and form VAT652 has gone

If your net error is over £50,000, or it is between £10,000 and £50,000 and exceeds 1% of box 6, you have to make a separate error correction notification. You are also allowed to use this route voluntarily for an error of any size that sits below the method 1 limits, which is often the smarter call.

The mechanics changed recently. From 8 September 2025 you can no longer correct errors in your VAT Return using form VAT652. The routes now are HMRC's online error correction service, or a notification in writing. Do not download an old copy of VAT652 from a third-party site and post it — check the current route on GOV.UK before you send anything.

Whichever route you use, the notification has to contain enough for HMRC to reconstruct what happened:

• how each error arose
• the VAT accounting period in which it occurred
• whether it was an input tax or an output tax error
• the VAT under-declared or over-declared in each VAT period
• your VAT registration number, if you are notifying in writing

Written notifications go to the VAT Error Correction Team at BT VAT, HMRC, BX9 1WR. HMRC's guidance says that if you do not hear back within 40 working days, you should contact the VAT Error Correction Team to check it arrived. Diarise that date when you send it. A notification that quietly went missing still leaves the VAT unpaid and the interest running.

Worked example: when the 1% test decides it

Nadia, commercial print business. Nadia discovers in her September quarter that a zero-rating decision on a run of customer brochures was wrong. Across five previous quarters she under-declared £14,800 of output tax. She also finds £1,900 of input tax she should have claimed on the same jobs. Total due to HMRC £14,800, total due to Nadia £1,900, so her net error is £12,900.

That sits between £10,000 and £50,000, so the 1% test applies. Box 6 on the return for the period in which she found the errors is £980,000. One per cent of that is £9,800. Her £12,900 net error exceeds it, so she cannot adjust on the return. Nadia must make a separate error correction notification.

Change one number and the answer flips. If Nadia had found the errors in a quarter with box 6 of £1,400,000, 1% would be £14,000, her £12,900 would sit under the line, and the same error would have been a return adjustment. Same mistake, same money, different route — purely because of which period she happened to spot it in. That is why the box 6 figure has to be the first thing you calculate, not an afterthought.

Deliberate errors: the thresholds simply do not apply

This is the part that turns an administrative job into a serious problem, and it is the single most expensive misunderstanding in this area. HMRC's rule is that you must always use method 2 if you made the errors on previous returns deliberately. There is no small-error exemption. A deliberate under-declaration of £900 goes down the same notification route as one of £90,000, and it must be notified in writing.

Deliberate does not require an elaborate scheme. Knowingly leaving a sale off a return because cash was tight that quarter, or claiming input tax on something you knew was personal, is a deliberate error. Netting it against a genuine input tax under-claim so the total falls under £10,000 and then quietly adjusting the next return does not make it go away. It adds a second problem on top of the first, because you have now used a route you were not entitled to use.

The other consequence is on time limits, covered next.

The four-year time limit — and the one exception

The time limit for error corrections is four years from the end of the prescribed accounting period in which the error occurred. There is a variation for under-claimed input tax, where the limit runs four years from the due date of the return for the prescribed accounting period.

Four years cuts both ways. It caps how far back HMRC will normally look, and it caps how far back you can reclaim VAT you overpaid. If you have found an old over-declaration, work out the deadline before you do anything else, because a claim that ages out is gone.

The exception: the four-year time limit does not apply to deliberate errors. There is no point in a business hoping a deliberate under-declaration from six years ago has expired. It has not.

Interest and penalties: what each route actually costs

Correcting an error does not switch off interest. HMRC's position is that late payment interest applies if an error means you did not pay all the VAT payable by the due date for that VAT period. That runs from the original due date, not from the day you noticed. Since 6 April 2025 the late payment interest rate has been the Bank of England base rate plus four percentage points; it was 7.75% from 9 January 2026, and it moves with the base rate, so check the current figure before you budget for it. Our late payment interest calculator will give you a rough figure for what the delay has cost.

Penalties are a separate question, and they turn on behaviour rather than on which method you used. If you took reasonable care and the return still contained an inaccuracy, HMRC will not charge a penalty. Where a penalty does apply it is a percentage of the tax, and the range depends on the behaviour and on whether you came forward yourself (unprompted) or only after HMRC started asking (prompted).

Those percentages are of the potential lost revenue, so on Nadia's £14,800 of under-declared output tax the difference between an unprompted careless disclosure at the bottom of the range and a prompted one is real money. Coming forward first is worth more than any amount of arguing later.

The traps that turn housekeeping into a disclosure

Trap one: assuming a method 1 adjustment counts as telling HMRC. It does not. HMRC states plainly that correcting errors using method 1 is not a disclosure for the purposes of the penalty rules. If your error was careless rather than an honest slip, adjusting the return does nothing for your penalty position. To get the reduction for an unprompted disclosure you have to separately tell HMRC about both the error and your grounds for seeking a reduction to the penalty. This catches out a lot of otherwise careful businesses: they fix the money and think the job is done, then find themselves at the prompted end of the range two years later.

Trap two: netting off errors that should be reported separately. The net error test is a legitimate calculation, not a licence to bundle. If part of what you are netting was deliberate, method 2 applies to the whole thing regardless of what the net figure comes to. Netting a deliberate under-declaration against a genuine input tax under-claim to slip under £10,000 is exactly the behaviour that pushes a case from careless into deliberate territory.

Trap three: using last quarter's box 6. The 1% test uses the box 6 declaration for the period in which you discover the errors. Not the period the error was in, and not an average. Seasonal businesses get this wrong routinely.

Trap four: treating routine adjustments as errors. Not everything is an error correction. Retail scheme annual adjustments, Capital Goods Scheme adjustments, credit notes and bad debt relief are ordinary accounting operations, not errors, and they do not go through the error correction procedures at all. Putting them through as errors muddies your record and can make a clean business look like a repeat offender.

Trap five: doing nothing because you are not sure. Interest runs either way, and an unprompted disclosure is always worth more than a prompted one. If you are unsure whether the 1% test is satisfied, notify separately. You are explicitly allowed to use method 2 for errors below the method 1 limits.

Getting your VAT house in order afterwards

Most VAT errors are not exotic. They are a rate applied wrongly to one product line, a deposit treated as outside the scope, or input tax claimed on an invoice that never met the requirements. If a supplier invoice is the weak point, the VAT invoice checker will tell you whether it carries what it needs to support a claim at all.

Rate changes cause the first category. If you sell food or run a leisure business, the VAT changes on children's meals and days out are worth reading before you set your tills, because a rate applied wrongly at the point of sale is what produces a five-quarter error later. On record-keeping, our Making Tax Digital guide covers how HMRC expects records to be kept and linked, which matters because a broken digital link is how small errors survive undetected for a year.

For why HMRC is looking harder at indirect tax, the tax gap figures for 2024-25 show where the compliance effort is going. And if the correction lands a company with a bill alongside its other liabilities, our guide to paying corporation tax covers the payment methods and reference formats.

The full rules are in VAT Notice 700/45 on GOV.UK. If your error is anywhere near the thresholds, or anywhere near the word deliberate, get an adviser to look at it before you file anything.