- The £90,000 VAT threshold is measured across a rolling 12-month period, not a fixed tax year.
- You must notify HMRC within 30 days of the end of the month in which your sales cross the limit.
- If a one-off spike caused the breach, you can apply to HMRC for a registration exception.
In the UK, compulsory VAT registration happens when your taxable turnover exceeds £90,000 across any rolling 12-month period. This formal limit never resets with your company accounting year or on 6 April when the personal tax year begins. Check every month. At the close of each calendar month, you add the newest turnover figure and drop the oldest month from your running twelve-month total.
This guide is for UK small-business owners, sole traders, and company directors trading near the £90,000 mark. Many founders check their revenue only once a year. Waiting for an annual review creates real risk. Spotting a breach months late brings backdated tax bills, interest charges, and late penalties from HM Revenue and Customs.
How the rolling 12-month period works
The rolling 12-month period is a moving window. It steps forward by one month at the end of each calendar month. The calculation looks backward across twelve full trading months. For instance, on 30 June, your rolling period covers 1 July of the previous year through 30 June of the current year.
When July ends, the window moves again. You drop the previous July figures from your total calculation. Then you add the new July figures to establish your updated twelve-month turnover.
This HMRC test repeats every thirty days. A business can trade safely below £80,000 for years, experience two busy trading quarters, and cross the line without noticing. If you already run a one-hour budget review, tracking rolling sales takes only five minutes.
Calculate taxable turnover across twelve months
Taxable turnover represents the total cumulative value of all sales subject to VAT across all VAT rates. Standard-rated items at 20 percent count. Reduced-rate goods at 5 percent count. In addition, zero-rated goods such as basic groceries and books count toward the £90,000 ceiling.
Turnover means gross sales, not net profit. It is your total sales revenue before you pay staff, materials, or bills. Do not subtract customer refunds unless you issued formal credit notes. Your billing schedule matters as well: if you set clear payment terms for cash flow, remember that the tax point date governs the test, not when the cash lands.
Some sales stay outside the calculation. VAT-exempt goods and services do not count toward the £90,000 limit. Common exempt areas include insurance, finance, and residential rent. You also leave out capital asset sales. Selling an old company van or office desk will not push you into mandatory VAT.
The 30-day rule and your effective registration date
When rolling sales pass £90,000, the clock starts. Your notice deadline runs from the end of the month you crossed the line, not from the exact invoice date.
Suppose your taxable sales cross £90,000 on 14 October, meaning the month officially concludes on 31 October. You have until 30 November to notify HMRC online. Missing that deadline triggers penalties.
Registration is not immediate. Under this historical rolling test, your official VAT start date is the first day of the second month after the threshold was breached. For an October breach, registration takes effect on 1 December. After that day, you must charge VAT on all taxable sales, issue valid invoices, and submit digital VAT returns.
Worked 12-month schedule: when to notify HMRC
A worked schedule illustrates how dropping older months shifts the running total. Examine the schedule below. In this practical example, an independent design firm reviews sales at the end of each consecutive calendar month.
Labelled example: An invented design firm tracks trailing twelve-month turnover across four monthly reviews.
| Review Date | Trailing 12-Month Period | Monthly Added | Monthly Dropped | Rolling Turnover | HMRC Action Required |
|---|---|---|---|---|---|
| 31 May | 1 June to 31 May | £7,200 | £5,100 | £84,500 | Under threshold; continue monthly check. |
| 30 June | 1 July to 30 June | £8,400 | £4,800 | £88,100 | Approaching threshold; prepare pricing review. |
| 31 July | 1 August to 31 July | £9,600 | £5,200 | £92,500 | Breached £90,000; register by 30 August. |
| 31 August | 1 September to 31 August | £7,000 | £6,000 | £93,500 | Effective registration date is 1 September. |
Look at the July review date. The firm added £9,600 and dropped £5,200 from the prior year. That pushed cumulative sales to £92,500. The 30-day clock started on 31 July, setting the notice deadline at 30 August. The official registration took effect on 1 September.
You must keep clear accounting records to support these calculation totals. As explained in our guide on how long to keep business records, HMRC requires small firms to preserve VAT records for at least six years.
Requesting an exception for temporary threshold spikes
Sometimes a single large order pushes a business past £90,000 for a brief period. Common examples include a large seasonal rush or a one-off consultancy fee. You might not need to register if this rise will not last.
You can ask HMRC for a registration exception. To qualify, you must show that your taxable turnover will stay below the £88,000 deregistration threshold over the next twelve months. You must submit your request in writing before your 30-day notice window ends.
HMRC evaluates exception requests on strict grounds. You must supply written explanations and realistic financial forecasts that prove your business will remain under £88,000. Approval comes in writing. If HMRC rejects your case, register immediately. As when checking contractual terms in our commercial payments checklist, preparing your figures early prevents costly compliance delays.
The forward-looking 30-day test
UK rules also include a separate forward-looking test. You must register if you expect your taxable sales to exceed £90,000 in the next thirty days alone. This rule captures rapid growth.
This situation often happens when a small firm wins a large project or signs a major retainer. The forward-looking test does not wait for the calendar month to close.
You have thirty days from the date of realization to notify HMRC. Your effective registration date is the day you formed that expectation rather than the start of the following month. Comparing this fast requirement with the quarterly rhythms in our guide to estimated taxes and safe harbours demonstrates why operators must monitor upcoming contracts continuously.
Sources and scope
GOV.UK: Register for VAT · HMRC: Who should register for VAT (Notice 700/1) · HMRC: VAT guide (Notice 700). This guide provides general tax information for UK operators. Tax law is complex. Always consult a qualified accountant regarding your specific circumstances.