Missed the 30-day window after crossing £90,000? Here's exactly what HMRC does next, how the penalty is calculated, and how to limit the damage.
Last updated: June 2026
You don't just pay a fine and move on — HMRC backdates your effective date of registration to the date you should have registered (30 days after crossing £90,000), and you owe VAT on everything you sold from that backdated date, whether or not you actually charged your customers VAT at the time. This is the part that catches people out: if you didn't add VAT to invoices during the period you were late, you generally still owe HMRC that VAT out of your own pocket, since you can't retroactively bill customers who've already paid.
On top of the backdated VAT itself, HMRC charges a failure to notify penalty calculated as a percentage of the VAT that was unpaid because you didn't register on time.
The penalty percentage depends on how late you were and whether the failure was "deliberate" or careless/non-deliberate, and whether the disclosure was prompted (HMRC found it) or unprompted (you told them first):
| Behaviour | Unprompted disclosure | Prompted disclosure |
|---|---|---|
| Non-deliberate (genuine mistake) | 0–30% | 10–30% |
| Deliberate but not concealed | 20–70% | 35–70% |
| Deliberate and concealed | 30–100% | 50–100% |
In practice, most late registrations are treated as non-deliberate — a business simply didn't realise it had crossed the threshold, or misjudged its rolling 12-month turnover. Coming forward voluntarily as soon as you realise (rather than waiting for HMRC to notice) meaningfully reduces the penalty percentage you're likely to face.
Legally, you can issue VAT-only invoices to VAT-registered business customers for the period you should have been charging VAT, and they can usually reclaim it. In practice this is awkward and many businesses choose not to for relationship reasons, especially with consumer customers who have no ability to reclaim VAT and would simply feel like they're being asked to pay more after the fact. Either way, you as the seller remain liable to HMRC for the VAT regardless of whether you successfully recover it from customers.
In addition to the failure to notify penalty, HMRC charges late payment interest on the VAT itself, calculated daily from when it was originally due until it's paid, at the Bank of England base rate plus a fixed margin. This runs independently of the failure to notify penalty and can add up meaningfully if the late registration spans many months.
Not automatically zero-tolerance, but it's the norm rather than the exception for HMRC to charge some penalty. The percentage depends heavily on whether you disclose the delay yourself and whether it was a genuine mistake. Some genuine, promptly-disclosed mistakes can end up with a 0% penalty at HMRC's discretion, but VAT and any interest are still due.
Generally yes. Your registration is backdated, and the VAT is deemed to be included in what you already charged, meaning you effectively pay it out of your own revenue rather than passing it on, unless you go back and separately invoice customers for it.
This is treated as "non-deliberate" behaviour, which carries the lowest penalty band (0–30%), especially if you disclose it yourself as soon as you notice rather than waiting for HMRC to find it during a check.
Yes, you can ask HMRC to review the decision and, if unsuccessful, appeal to the tax tribunal. Reasonable excuse defences (genuine unforeseeable circumstances) can sometimes reduce or remove a penalty, but simply not knowing the rules is generally not accepted as a reasonable excuse on its own.
Track your rolling 12-month taxable turnover regularly, not just at your accounting year end — it's a moving window, not a fixed annual figure. Our VAT threshold checker and deadline tracker can help you monitor this on an ongoing basis.
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