Self-Employed Personal Trainer Tax
Written and reviewed by the Personal Trainer Accountants editorial team. Last reviewed 8 August 2026.
Most personal trainers become self-employed by accident rather than by decision. You pick up a few clients alongside a gym job, it grows, and at some point you are running a business without ever having registered one.
The tax position is not complicated, but the deadlines are unforgiving and two of them carry automatic penalties. This page sets out what has to happen and when.
Registering With HMRC
If your gross self-employed income goes over £1,000 in a tax year you have to tell HMRC. The deadline is 5 October following the end of that tax year, so income earned in the year to 5 April 2026 has to be notified by 5 October 2026.
Registering is separate from filing. Plenty of trainers know about the January deadline and have never heard of the October one, then find they registered late on top of everything else. Do it as soon as you know you are over, not when the return is due.
The Trading Allowance
The first £1,000 of gross trading income is covered by the trading allowance. Below that, and with no other reason to file, you generally do not need to register at all.
It is worth understanding what the allowance costs you though. If you claim it, you cannot deduct any other expenses or allowances. A trainer with £900 of income and £400 of costs is better off with the allowance. A trainer with £900 of income and £1,200 of costs, which is common in a first year, may want to register anyway in order to claim the loss, and there are other reasons to register voluntarily including protecting a National Insurance record and claiming Tax-Free Childcare or Maternity Allowance.
National Insurance for Trainers
For 2026 to 2027, Class 2 National Insurance is treated as having been paid once profits reach £7,105, which protects your National Insurance record without you paying anything. Below that figure you can choose to pay voluntary Class 2 at £3.65 a week, and it is often worth doing, because gaps in the record affect the state pension.
Class 4 is the one that costs money. It runs at 6% on profits between £12,570 and £50,270, and 2% above £50,270. It is collected through the self assessment return rather than separately, which is why a first tax bill is usually larger than a trainer has budgeted for: it is income tax and Class 4 together, plus possibly a payment on account towards the following year.
Making Tax Digital From April 2026
Making Tax Digital for Income Tax started on 6 April 2026 for anyone whose qualifying income in the 2024 to 2025 tax year was over £50,000. It replaces one annual return with quarterly updates to HMRC, kept in software rather than a spreadsheet at year end.
The threshold falls to £30,000 from 6 April 2027, measured on 2025 to 2026 income, and to £20,000 from 6 April 2028, measured on 2026 to 2027 income. A trainer earning £25,000 today is outside it now and inside it in two years, which is a reason to get the record keeping right before it becomes compulsory rather than after.
Exemptions exist, including for people who are digitally excluded. The conditions sit on HMRC's own guidance and are not summarised here because we have not read them in full.
Deadlines and Penalties
For the 2025 to 2026 tax year: register by 5 October 2026, file a paper return by 31 October 2026, or file online by 31 January 2027. The tax is due on 31 January 2027 as well, and if you make payments on account the second one falls on 31 July.
The filing penalty is automatic. It does not wait for HMRC to notice and it does not care that the return would have shown no tax to pay. If the money is not there in January, file anyway and deal with the payment separately, because filing late and paying late are two different penalties and there is no reason to collect both. HMRC sets the dates out on its Self Assessment deadlines page, and the National Insurance position is on its self-employed National Insurance page.