Crossing the VAT threshold: the two tests, the 30-day trap, and the exception worth claiming
Most owner-managed businesses meet VAT registration late and by accident, because the rules are counter-intuitive in exactly two places. A walk through both tests as a growing business meets them: the rolling twelve-month backward test, the harsher thirty-day forward test, and the one-off-spike exception that is easy to miss, plus what counts towards the £90,000 and what lateness costs.
Two tests, and only one of them is forgiving
Two things can make a business liable to register, and they behave very differently. The backward-looking test asks what you have already sold; the forward-looking test asks what you are about to sell. Both turn on the same figure: taxable turnover of £90,000, the threshold since 1 April 2024 and still the figure in force today. The deregistration threshold sits just beneath it at £88,000, the gap kept deliberately so businesses near the line are not forced to register and deregister repeatedly. The backward test gives you a month or so of breathing room. The forward test does not. It can make you VAT-registered as of a date already passed, for invoices you have already sent with no VAT on them. What follows is general information, not advice on your own circumstances.
What actually counts towards the £90,000
Taxable turnover is not your accounting turnover, and this is where people first go wrong. It is the value of everything you sell that is not exempt and not outside the scope of VAT. Crucially, that includes zero-rated supplies, which carry VAT at zero per cent but are still taxable. A children's clothing retailer can sit well past the threshold while charging no VAT at all, and still must register. Reduced-rated supplies at five per cent count too. So do goods you hire or loan to customers, goods bartered, part-exchanged or given as gifts, and business goods used for personal reasons. Services bought from businesses in other countries that you must reverse charge count towards your own threshold, which surprises consultancies with foreign software subscriptions. What does not count: exempt supplies such as insurance, the granting of credit, and much education and health provision; income outside the scope of VAT; and disposals of capital assets, so selling a van or a machine does not by itself push you over. The exception, under paragraph 1(8) of Schedule 1 to the Value Added Tax Act 1994, is an interest in land supplied on a taxable supply that is not zero-rated, most obviously a building over which you have opted to tax.
The backward test runs on a rolling ruler
The trap is in the word rolling. At the end of every single month you must look back over the previous twelve months, not your accounting year, and add up your taxable turnover. If any of those rolling windows goes over £90,000, you are liable. A business with a March year end can breach it in the twelve months to 31 August and never know, because nobody adds anything up until the accounts are prepared the following spring. Two dates then follow. You must notify HMRC within thirty days of the end of the month in which you went over, and registration takes effect from the first day of the second month after you go over. Suppose a joinery business finds its taxable turnover for the twelve months ending 31 August 2026 came to £91,400. It must tell HMRC by 30 September 2026, and it is registered from 1 October 2026. Everything invoiced from that date carries VAT; everything before it does not.
The 30-day test, and the trap inside it
The forward test is the one that catches people badly. It applies where, at any time, you expect the value of your taxable supplies in the next thirty-day period alone to go over £90,000. Not cumulatively with what you have billed this year: in that window alone. You must register by the end of that thirty-day period, and here is the harsh part: registration takes effect from the beginning of that period, the date you realised, not the date the money came in. So if you sign a contract on 4 May 2026 that you reasonably expect will produce £95,000 of standard-rated work inside the following month, you are registered from 4 May 2026. An invoice you raised on 12 May without VAT is one you must now correct, and if the customer will not pay the extra twenty per cent, that comes out of your margin.
The exception worth claiming
There is statutory relief for the business that breaches the backward test because of a genuine one-off spike, and it is easy to miss. Paragraph 1(3) of Schedule 1 to the Value Added Tax Act 1994 provides that you do not become liable to register if HMRC is satisfied that your taxable supplies in the following twelve months will not exceed the deregistration threshold of £88,000. That is exception from registration, a real HMRC decision, not something you can assume. You apply by telephoning HMRC to request form VAT1, saying you want exception, then completing VAT1 and form VAT5EXC and returning them. HMRC says it will write to you within forty working days. The guidance sets out no prescriptive evidence list, so the burden is on you: the event that caused the spike, why it will not recur, and a credible forecast below £88,000. The comparison is against £88,000, not £90,000, so a business expecting £89,000 does not qualify. And exception is not exemption; you must keep watching your turnover, and if HMRC refuses you are registered from the original date.
Why splitting the business is the wrong answer
Somebody will suggest running the takeaway through one entity and the restaurant through another, so each stays under £90,000. HMRC attacks this directly. Paragraph 1A of Schedule 1 to the Value Added Tax Act 1994 exists to prevent an artificial separation of business activities carried on by two or more persons from resulting in an avoidance of VAT, and in judging whether a separation is artificial, regard is had to how closely those persons are bound by financial, economic and organisational links. Where the conditions in paragraph 2 are met, HMRC issues a Notice of Direction treating the entities as a single taxable person. The point most people miss is what HMRC must prove, and its own manual puts it plainly: it need not prove an intention to avoid VAT, only that the artificial separation resulted in an avoidance of VAT. Shared premises, shared staff, one till, one bank account, one set of marketing, and one person making every decision are the links that decide these cases. Genuinely distinct businesses are a different matter.
What you can reclaim, and what lateness costs
Registering is not purely a cost. Regulation 111 of the Value Added Tax Regulations 1995 lets you recover input tax on things bought before your effective date of registration, on two clocks. For goods, you can go back four years, provided they are still on hand at the registration date and will be used in the registered business: stock, tools, equipment, vehicles. For services the window is only six months, so the accountancy fees and website build bought seven months ago are lost. The claim must go on the first return you are required to make, and you need the invoices. Lateness has a defined price. A failure to notify penalty is a percentage of the potential lost revenue. Non-deliberate and unprompted within twelve months, the range runs from zero to thirty per cent. Unprompted after twelve months, or prompted within twelve months, ten to thirty. Prompted after twelve months, twenty to thirty. Deliberate failures run twenty to seventy per cent unprompted and thirty-five to seventy prompted; deliberate and concealed, thirty to one hundred unprompted and fifty to one hundred prompted. You still owe the VAT.
Four things to do this month
First, compute a rolling twelve-month taxable turnover figure at each month end, including zero-rated sales and excluding exempt income and capital disposals. Second, set an internal alarm at around £75,000 on the rolling figure, which buys you time to decide rather than react. Third, before signing any contract that is large relative to your normal month, ask whether its supplies fall within a single thirty-day period. Fourth, if you have already breached because of a one-off, take the exception seriously before defaulting to registration. Three questions for your accountant: what is my rolling twelve-month taxable turnover at the last month end; do I have pre-registration goods on hand from the last four years, or services from the last six months, whose invoices I should collect now; and if I register, does my customer base absorb VAT or does it fall on my margin. That last answer is usually worth more than the compliance itself.
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This article is general information only and does not constitute tax advice. Figures and dates are current as at the date of writing; any worked example is illustrative. Always consult a qualified adviser before acting.