How this is calculated
Compulsory VAT registration is triggered in two ways: first, if your taxable turnover for any rolling 12-month period (not a fixed tax year) exceeds the registration threshold; second, if at any point you expect your taxable turnover in the next 30 days alone to exceed the threshold, for example due to a single large contract.
This calculator compares both figures against the current threshold and tells you which test, if any, is breached, along with how much headroom you have left on the rolling 12-month test.
Taxable turnover includes standard, reduced and zero-rated sales, but excludes VAT-exempt income and sales of capital assets; getting this classification right is often the trickiest part of the assessment.
Why the rolling 12-month test catches people out
Many businesses only check their turnover against the threshold once a year, at their accounting year end, but the legal test looks back over any rolling 12-month window, meaning you could breach the threshold mid-year without realising until it is too late.
If you fail to register when required, HMRC can still charge VAT on sales made from the date you should have registered, along with potential penalties, even if you never actually charged customers VAT at the time.
Voluntary registration and deregistration
You can register voluntarily below the threshold, which allows you to reclaim input VAT on purchases, and can improve credibility with VAT-registered business customers, though it also means charging VAT to customers who cannot reclaim it, such as members of the public.
Once registered, you can apply to deregister if your taxable turnover for the next 12 months is expected to fall below the deregistration threshold, though HMRC will review the application before agreeing.
What this means for your company
Treat the result as a planning figure for the 2026/27 tax year. If it changes what you were about to do, take a director's salary, a dividend, a large asset purchase or a filing decision, check it against your own accounts first. We can review the position with you and confirm the tax treatment before you commit.
Frequently asked questions
Is the VAT threshold based on the tax year or a rolling period?
It is based on any rolling 12-month period, checked continuously, not a fixed tax or calendar year. You need to review your turnover regularly, ideally monthly, to catch a breach as soon as it happens.
What happens if I register for VAT late?
HMRC can require you to account for VAT on sales from the date you should have registered, even if you did not charge customers VAT at the time, and may also charge a penalty based on how late the registration was and the VAT due.
Should I register for VAT voluntarily before I reach the threshold?
It depends on your customers: if they are VAT-registered businesses that can reclaim VAT, voluntary registration lets you recover input VAT on your own costs with little downside. If your customers are mostly the public, VAT will increase your effective prices or squeeze your margin.
Does all my income count towards the VAT threshold?
No, only taxable turnover counts, which includes standard, reduced and zero-rated sales. VAT-exempt income (such as some financial, insurance, and residential property income) and the sale of capital assets are excluded from the threshold calculation.