Do I have to register for VAT in the UK?

The £90,000 threshold, in plain English

The current UK VAT registration threshold is £90,000 of taxable turnover. It's been at that level since 1 April 2024, and it stays at £90,000 for the 2026/27 tax year.

The crucial word here is taxable. That includes:

• Standard-rated sales (20%)
• Reduced-rated sales (5%)
• Zero-rated sales (0%), yes these count even though no VAT is charged

It does not include VAT-exempt sales (like most insurance, education, or financial services) or the sale of capital assets you've kept for your own business.

Two tests, not one: how HMRC decides you must register

HMRC uses two separate tests, and either one can trigger compulsory registration.

Test 1: the historical (rolling 12-month) test

At the end of every calendar month, you check your taxable turnover for the previous 12 months. If it has gone over £90,000, you must notify HMRC within 30 days of the end of that month. Your effective VAT registration date is then the first day of the second month after you crossed the threshold.

The trap most businesses fall into: HMRC doesn't measure against your accounting year. The 12-month window slides forward every month. You can be safely under £90k in March and over £90k in April purely because of which months drop off the back.

Test 2: the future (forward-look) test

This one catches a lot of growing businesses by surprise. If at any point you have reasonable grounds to believe your taxable turnover will exceed £90,000 in the next 30 days alone (for example, you've just signed a large project contract), you must register immediately.

Your effective registration date is then the start of that 30-day period, not the end. This means you may need to register and start charging VAT before you've even received the income.

Where this gets ambiguous: "reasonable grounds to believe" isn't a hard test. A signed contract is clear. A verbal commitment from a client, a strong sales pipeline, a likely-to-convert tender, these are exactly the kind of grey areas where two reasonable people read the same facts and reach different conclusions. If you're not sure, this is the moment to ask a specialist, not to wait and see.

What if you only cross the threshold temporarily?

If you breach £90,000 just once because of a one-off spike (a single large contract, a seasonal peak), you can apply for an exception from registration. To succeed, you need to show HMRC that your taxable supplies will stay below the deregistration threshold of £88,000 in the following 12 months.

This isn't automatic. You apply, HMRC reviews, HMRC writes back. You should not assume the exception will be granted, and you should not delay registering on the assumption that it will be.

The expensive mistake we see: a business crosses the threshold by £2,000 in one month, decides "it's only temporary, I'll apply for the exception", waits three months, gets refused, and ends up owing backdated VAT on every sale during that wait, plus a penalty. The exception is real, but applying for it doesn't pause your registration deadline.

The cost of registering late

Late registration is one of the most expensive mistakes you can make in UK VAT. If HMRC catches up with you (and in 2026, they often do, through data-matching from marketplaces, banks, and tax filings), you'll typically face:

1. Backdated VAT on every sale you should have charged VAT on, even though you didn't actually collect it from the customer. That comes straight out of your margin.
2. A failure-to-notify penalty, calculated as a percentage of the VAT you should have paid. The percentage varies based on whether the failure was deliberate, careless, or unprompted, but it can reach 100% in the worst cases.
3. Interest on the late VAT, charged daily.

In practice, a business that registers six months late on £30,000 of taxable turnover could easily owe £6,000 in backdated VAT plus a penalty and interest. The penalty is reduced if you make an unprompted disclosure, so it always pays to come forward proactively if you've missed the deadline.

When does voluntary registration make sense?

You don't have to wait until £90,000. You can register voluntarily at any taxable turnover (even £0), and there are three situations where it can genuinely make sense.

1. You sell mostly to other VAT-registered businesses

Your B2B customers reclaim the VAT you charge them, so the 20% on top doesn't hurt your competitiveness. Meanwhile, you can reclaim VAT on your own costs (software, equipment, professional fees) and that's a real cash benefit.

2. You have significant input VAT to reclaim, especially upfront

If you've recently invested heavily in equipment, stock, or pre-launch costs, voluntary registration lets you reclaim that VAT. You can even claim pre-registration VAT on goods bought up to 4 years before registration (still in use) and services bought up to 6 months before, on your first VAT return.

3. You want the credibility of being VAT-registered

Some buyers, especially larger companies, treat non-VAT-registered suppliers as a sign of "very small business", which can affect tendering. This is softer than the financial arguments above, but it matters in some sectors.

What you need to do, step by step

1. Track your rolling 12-month taxable turnover at the end of every month. Don't wait for your year-end. A simple spreadsheet works.
2. If you cross £90,000: notify HMRC within 30 days through your Government Gateway account (or apply for exception if it was a one-off).
3. If you expect to cross it in the next 30 days: register immediately, with an effective date at the start of that 30-day period.
4. HMRC will issue your VAT registration certificate (form VAT4) with your VAT number, typically within 30 working days.
5. From your effective registration date, charge VAT on all taxable sales, keep digital records, and prepare to file quarterly returns under Making Tax Digital.

The situations that most often turn into costly mistakes

The £90,000 line has more grey zones than people realise, and the cost of getting it wrong is real. In practice, the situations below are where businesses most often end up paying backdated VAT, penalties, or both:

• You're not sure whether some of your income is taxable, zero-rated, or exempt (this is more common than you'd think, especially in mixed-supply businesses, education, training, or property)
• You think you may have already missed the registration date and want to understand the unprompted disclosure route
• You're considering voluntary registration and want a clear-eyed view of whether it actually helps in your case
• You're growing fast and want to plan around the threshold (whether to push through it, time large contracts, restructure, etc.)
• You've received a letter from HMRC about your VAT registration status and you're not sure how to respond

Whether you're a business owner or an accountant working on a client case, we focus on the VAT questions where extra expertise pays off, and we work in plain English.