VAT isn't about how much profit you make — it's about turnover
This trips up a lot of self-employed people. VAT has nothing to do with your profit, your take-home pay or how well you're doing. It's driven purely by your taxable turnover — the total sales you invoice for VATable work. You can be barely breaking even and still be legally required to register.
The number that matters is £90,000. Once your taxable turnover goes over that in any rolling 12-month period, registration is compulsory and the clock starts ticking. Below it, registering is your choice — and sometimes a smart one. Below we walk through the threshold, the rolling test that catches people out, voluntary registration, and whether the Flat Rate Scheme is worth the hassle.
What this guide covers
- The £90k threshold and how the rolling 12-month test really works
- When voluntary registration actually helps (and when it just adds admin)
- How the Flat Rate Scheme works and who it suits
- What changes day-to-day once you're VAT registered
The £90,000 threshold, explained properly
You must register for VAT once your taxable turnover exceeds £90,000 in any rolling 12-month window (check the current rate — the threshold does move from time to time). The key word is rolling. This is not your tax year and it's not your accounting year. At the end of every single month you look back over the previous 12 months and add up your taxable sales. The moment that running total tips over £90,000, you're caught.
There's also a second test: if you expect to go over £90,000 in the next 30 days alone — say you've just landed one big contract — you have to register straight away, based on that expectation.
Watch the deadline. Once you cross the threshold you have 30 days to register, and your registration takes effect from the first day of the second month after you went over. Miss it and HMRC can charge you VAT you never collected from customers, plus penalties. Register on time and it's painless.
What counts towards the £90k?
Taxable turnover means your standard-rated (20%), reduced-rated (5%) and zero-rated sales. It does not include genuinely exempt income (some finance, insurance and education) or things that aren't part of your trade, like the sale of a private car. If most of what you do is standard-rated services — a freelancer, a contractor, a trades person billing labour and materials — assume nearly all of it counts.
Voluntary registration: when it actually helps
You can register voluntarily below £90,000. It's worth considering when:
- Your customers are VAT-registered businesses. They reclaim the VAT you charge, so adding 20% doesn't put them off — and you get to reclaim VAT on your own costs.
- You buy a lot of VATable stock, tools or equipment. Registration lets you reclaim that input VAT.
- You want to look established. Some larger clients quietly assume a supplier under £90k is very small.
It's usually a bad idea when your customers are the public or other non-registered small businesses — because to them your prices just went up 20% overnight and they can't claim it back.
The Flat Rate Scheme
The Flat Rate Scheme (FRS) is a simplification for smaller businesses (broadly those with VATable turnover up to £150,000 when they join). Instead of tracking VAT on every purchase, you charge your customers the normal 20% but pay HMRC a single fixed percentage of your gross (VAT-inclusive) turnover. The percentage depends on your trade sector.
The trade-off: it's far less admin, and if your costs are low you can come out slightly ahead — but you generally can't reclaim VAT on purchases (bar certain capital assets over £2,000). There's also a "limited cost trader" rate that applies if you spend very little on goods, which wipes out most of the benefit, so check where you'd fall before assuming FRS pays.
Worked example. Say you're a consultant billing £6,000 + VAT in a quarter. You charge the client £7,200 (£6,000 + £1,200 VAT). On standard VAT you'd hand over £1,200 less whatever VAT you reclaim on costs. On a 14.5% flat rate you'd pay 14.5% of £7,200 = £1,044 to HMRC and keep the difference — but you can't reclaim VAT on your laptop, software or train fares. If your costs are high, standard VAT usually wins; if they're tiny, FRS can edge ahead. Run your own numbers before choosing.
Life after registration
Once registered you must: add VAT to your invoices, keep digital VAT records, and file VAT returns (usually quarterly) through MTD-compatible software. You'll pay over the VAT you've collected, minus the VAT you've reclaimed. It's not hard once it's set up — but it's a genuine ongoing commitment, which is exactly why it's worth getting the decision right rather than drifting into it.
If you're also weighing up quarterly reporting more broadly, it's worth reading our guide on the self-employed tax-deadline calendar so VAT returns don't collide with your other deadlines. And if you're in construction, VAT sits alongside the rules in our CIS guide — the two interact, so don't look at either in isolation.
Not sure whether you're about to cross the line, or whether voluntary registration or the Flat Rate Scheme would leave you better off? This is exactly the kind of thing that's cheap to get right early and expensive to get wrong. Get started with us and we'll look at your actual numbers.
