Register, file, pay

  1. Register for Self Assessment if your gross trading income is over £1,000 in a tax year. Deadline to tell HMRC is 5 October after that year ends (5 October 2026 for 2025/26).
  2. Keep income and expense records as you go. HMRC can ask for them for at least five years after the 31 January filing deadline.
  3. File the online return by 31 January 2027 for 2025/26 (paper was 31 October 2026). Pay the balancing payment the same day.
  4. If last year’s bill was over £1,000, Payment on Account is due 31 January and 31 July, each 50% of that bill.

Full deadline calendar and penalty ladder.

What goes on the self-employment pages (SA103)

Turnover is everything clients paid you, including cash and including amounts an app passed on. Commission is an expense if you declared the gross. Products and mileage in the usual boxes. This is often a short return. Short is fine. Blank is not.

Deadlines and penalties

Miss the online deadline and the late-filing penalty is £100 immediately, even if you owe no tax. After three months it is £10 a day (capped at £900). At six and twelve months HMRC add 5% of the tax due or £300, whichever is greater. Late payment is a separate 5% at 30 days, six months and twelve months, plus interest.

Mistakes cleaners make on the return

  • Ignoring cash because it never hit the bank.
  • No total for the year, guessing £12,000 because it “sounds about right”.
  • Claiming the trading allowance and also products and mileage. One or the other.
  • Not filing because profit was under the personal allowance. You may still need the return, and Class 4 can still apply above £12,570 profit.
  • Stopping work in June and never telling HMRC, then collecting penalties on returns you did not know were still due.

If your profit is under £1,000 of expenses you might use the trading allowance instead of listing products and mileage. Work both numbers. Use the one that leaves you with less profit. You cannot use both.

← Cleaner tax overview · Expenses · Do I need to register?

Common questions

I have no National Insurance number on a letter, only cash. Can I still register?

You register with HMRC using your NI number and identity. Cash work is not a reason to stay off the books. It is a reason to start a notebook today.

Should I use the £1,000 trading allowance?

If your real expenses are under £1,000, probably. If you drive a lot between jobs, mileage alone can beat it. Add it up.