The £90k VAT Threshold: The Rolling 12-Month Test and Forward-Look Rule for 2026

The £90,000 UK VAT registration threshold is the single most-misunderstood number in UK small business taxation. The threshold is not measured against the calendar year, not against the company's financial year, but against any rolling 12-month period. A growing business can cross the threshold mid-year without the annual figures looking alarming. Compounding the confusion, there is a second forward-look test: if you reasonably expect to cross £90,000 in the next 30 days alone (typical for a contract win or seasonal spike), VAT registration is triggered immediately by that expectation, not by the historic numbers.

This piece walks both tests, the 30-day registration window, the late-registration penalty regime, and the exception rules that excuse certain businesses from registration even above threshold. Sister pieces in the UK VAT registration hub cover voluntary VAT registration for B2B startups and the 2026 VAT grouping rule changes.

The historic rolling 12-month test

At the end of each calendar month, look back at the previous 12 months' VAT-taxable turnover. If the total exceeds £90,000, VAT registration is required within 30 days of the end of that month. The registration takes effect from the first of the following month.

Worked example: a business has monthly turnover figures showing £8,000 in April, £8,500 in May, then a £12,000 spike in June. By end of June, the rolling 12-month total has crossed £90,000 for the first time. Registration must be submitted by 30 July, with VAT registration effective from 1 August. The 30-day window is firm; missing it triggers late-registration penalties on top of the back-VAT due.

The forward-look 30-day test

If at any point you have reasonable grounds to expect that VAT-taxable turnover in the next 30 days alone will exceed £90,000, registration is required immediately, with the effective date being the date the expectation arose. The forward-look test typically applies to: a large contract win, a major project award, a seasonal business entering peak season, or a major commercial event.

Worked example: a small consulting business with £15,000-£20,000 of monthly turnover wins a £120,000 single-project contract on 10 May. From the moment the contract is signed, the forward-look test is triggered (the next 30 days alone will exceed £90k from that single contract). Registration must be effective from 10 May, not from the end of May or June.

Side-by-side: the two tests

What counts as VAT-taxable turnover

VAT-taxable turnover is the total of all standard-rated, reduced-rated, and zero-rated sales. Exempt supplies (insurance, financial services, education, healthcare) do not count. Sales outside the UK's VAT scope (services to non-UK B2B customers, certain digital services to non-UK consumers) typically do not count, though the rules vary by supply type. Non-trading income (interest, dividends, capital gains, grants) does not count.

Late registration penalties

A business that registers late owes VAT on all sales made from the date registration should have started, even if no VAT was charged to customers. HMRC also imposes a "failure to notify" penalty calculated as a percentage of the under-paid VAT, ranging from 0% (unprompted disclosure with reasonable excuse) to 100% (deliberate non-registration discovered by HMRC). The penalty regime is described in Schedule 41 Finance Act 2008.

A common pattern: a business is six months late registering and has invoiced £80,000 of taxable sales in that period without charging VAT. The business owes HMRC £13,333 of back-VAT (1/6 of £80,000, i.e., the VAT element that should have been charged at 20%), plus interest, plus a failure-to-notify penalty typically 10-30% of the back-VAT for a careless rather than deliberate error.

The exception rule

A business that crosses the threshold but reasonably expects turnover to fall below £88,000 (the deregistration threshold) in the next 12 months can apply for "exception from registration" within 30 days of the crossing. HMRC must grant the exception if satisfied; in practice it is granted where the cause of the threshold crossing was a one-off event (large single contract, asset disposal) and ongoing turnover will be below £88k. The application requires evidence of the expected drop; speculative applications are rejected.

How to register

Should I delay crossing the threshold?

For some B2C businesses (consumer retail, hospitality, services to private customers), staying just below the threshold has a real financial benefit because charging VAT adds 20% to the price for customers who cannot recover it. The "VAT cliff" effect distorts behaviour: businesses limit growth, decline orders, or split into multiple legal entities to stay below £90k. HMRC actively investigates artificial splitting (the "disaggregation" rule), so the structural avoidance route is risky. Most growing businesses cross the threshold and absorb the VAT cost rather than constrain growth.

Will the threshold change?

The £90,000 threshold has been static since April 2024. Before that it sat at £85,000 from April 2017 to April 2024. The threshold is not index-linked, so inflation drags more businesses into VAT each year. Any change to the threshold requires legislation; rumours periodically circulate about a major reduction (to £20k or £30k, in line with EU norms) but no such legislation has been brought forward in recent budgets.

What if I am over the threshold but not registered?

If you discover you have been over the threshold for some time without registering, the cleanest route is unprompted voluntary disclosure to HMRC. The disclosure typically results in: registration backdated to the correct date, back-VAT plus interest paid, and a failure-to-notify penalty of 10-30% of the back-VAT (for careless error). HMRC discovering the failure first results in penalties materially higher (typically 35-100%), so unprompted disclosure is strongly preferable. A specialist VAT accountant handles the disclosure and registration in parallel.

What if I just crossed the threshold but my business is shrinking?

If you crossed the threshold this month but your ongoing trajectory is downward, apply for exception from registration within 30 days, with evidence of the expected drop. If HMRC grants the exception, no registration is needed and the threshold is reset for the next 12 months. If HMRC refuses, the standard 30-day registration window applies. The exception application is free; HMRC reviews and decides within 30-45 days typically.