UK VAT threshold 2026: a complete guide for growing businesses

It’s a good feeling knowing that your business is growing. However, it can be less welcome to learn that, once your taxable turnover crosses the UK VAT threshold of £90,000, you’re legally required to register for VAT. When this happens, the clock starts ticking whether you’re watching it or not.

From 1st April 2026, the registration threshold remains at £90,000 and the deregistration threshold remains £88,000. Those figures won’t surprise many business owners. What does catch people out is how the threshold is calculated, and what happens when they fail to register.

This guide covers everything you need to know. We look at the rolling 12-month rule, the less well-known “forward-look” test, what to do if you breach the threshold only temporarily, late registration penalties, and why voluntary registration is sometimes the smarter move.

Key figures at a glance

The “rolling 12-month” UK VAT threshold trap

This is where many businesses run into trouble. HMRC doesn’t assess your turnover against your accounting year. Instead, it uses a rolling 12-month window that moves forward by one month at the end of every calendar month.

That means you should be checking your total taxable turnover for the previous 12 months at the end of every calendar month — not once a year at year-end.

If that rolling total exceeds £90,000 at the end of any month, you must notify HMRC within 30 days of the end of that month. Your effective date of registration — the date from which you must charge VAT — is the first day of the second month after you went over.

Example. At the end of August 2026, you find your taxable turnover for the 12 months to 31 August has exceeded £90,000. You must notify HMRC by 30 September. Your effective registration date is 1st October 2026. This is the date from which VAT must be charged on your sales.

The table below shows how the window slides forward each month. The highlighted row shows the month a hypothetical business crosses the threshold.

The “forward-look” rule (or the 30-day surprise!)

Most business owners are aware of the rolling look-back rule. Fewer know about the forward-look test. This can catch even well-run businesses off guard.

This rule means that you must also register if you have reasonable grounds to believe that your taxable turnover will exceed £90,000 in the next 30 days alone. This is an entirely separate test from the rolling 12-month rule. It applies even if your historic turnover is well below the threshold.

Scenario. Imagine that, on 10th June 2026, you agree to provide services under a new contract. You have reasonable grounds to think that the taxable supplies you will make under that contract in the next 30 days will alone exceed £90,000. In this instance, the trigger is not when payment arrives — it is the moment you have reasonable grounds to believe your taxable supplies will exceed the threshold in the coming 30 days. From that date, you must register by the end of the 30-day period, and your effective date of registration is 10th June 2026.

The practical point. If you’re in discussions about a large contract that would push your taxable supplies over the threshold in a single month, take VAT advice before committing.

What if you only breach the UK VAT threshold temporarily?

Crossing the £90,000 UK VAT threshold does not automatically mean you must register if the breach is temporary. HMRC allows a business to apply for an exception from registration if it can demonstrate that taxable supplies will not exceed the deregistration threshold of £88,000 in the 12 months following the breach.

To apply for exception from registration, you need to contact HMRC by telephone and request form VAT1 and form VAT5EXC. You then return both forms with evidence supporting your forecast turnover. HMRC will then confirm whether the exception is granted. If it is not, HMRC will register you for VAT.

A common scenario is when a business completes an unusually large one-off project or has an unusually busy period. If you can show that the spike is genuinely exceptional, and that ongoing taxable supplies will remain below the deregistration threshold, HMRC may grant an exception from registration. If in doubt, take advice before assuming you must register — or assuming you don’t have to.

What happens if you register late?

Late VAT registration carries two distinct financial consequences that compound each other.

First, HMRC backdates your registration to the date you should have registered. You become liable for VAT on all taxable sales made since that date — even if you didn’t charge it to your customers. If your customers are VAT-registered, you can issue a VAT-only invoice and recover the amount from them retrospectively. If they are not, the VAT liability falls on you. Either way, there is likely to be an impact on your cash flow.

Second, HMRC applies a failure-to-notify penalty under Schedule 41 of the Finance Act 2008. The penalty is calculated as a percentage of the potential lost revenue — the net VAT that should have been paid for the period of non-registration. The actual percentage depends on the degree of culpability, on whether the disclosure is prompted or unprompted, and on how quickly and fully you cooperate. The ranges are:

• Non-deliberate failures. 0–30% depending on timing and whether the disclosure is prompted or unprompted. Where there is a reasonable excuse, HMRC will not charge a penalty.
• Deliberate failures. 20–70%
• Deliberate and concealed failures. 30–100%

There is a 20-year time limit for HMRC to assess a failure-to-notify liability. HMRC may identify late registrations when reviewing annual accounts or Self-Assessment Tax Returns, but the responsibility to notify rests entirely with the business.

If you believe you should have registered earlier, notify HMRC promptly. The quality of disclosure — how quickly, fully and cooperatively you come forward — directly affects where within the penalty range HMRC will assess you.

When to consider voluntary registration

VAT registration is not only a compliance obligation — it can also be a deliberate commercial choice. Voluntary registration is available to any business with taxable turnover below the UK VAT threshold of £90,000, and there are situations where it makes clear financial sense.

Consider voluntary registration if:

• Your customers are predominantly VAT-registered businesses. They can reclaim the VAT you charge, so adding 20% to your invoices doesn’t increase their real cost.
• You have significant VAT on your own purchases — equipment, materials, professional fees. Registration allows you to reclaim that input tax.
• You want to project a more established image to larger B2B clients who may be reluctant to use an unregistered supplier.
• You are approaching the threshold and want to get your systems and processes in place before compulsory registration applies.

The case against voluntary registration is equally worth considering. If your customers are primarily end-consumers who cannot reclaim VAT, adding 20% to your prices either reduces your margin or makes you less competitive. The additional administrative burden — quarterly returns, digital record-keeping under MTD for VAT, careful invoice management — also has a real cost.

Our VAT services team can help you understand the impact for your specific business and advise on whether the numbers stack up.

Not sure where you stand?

If you’ve calculated your rolling turnover and worried you’re hovering near the limit, don’t wait for an HMRC letter. Our VAT experts can review your figures and handle the registration process for you. Get in touch today.