Guides · Updated 13 October 2026

Self Assessment for locums. The dates, and what to keep.

If you locum as a sole trader, nobody takes tax from your fees before they reach you. You report the year to HMRC yourself through Self Assessment. These are the dates and the records that make it straightforward.

An open planner on a desk

Registering

You can start working for yourself straight away. Once you earn more than £1,000 from self-employment in a tax year you must register for Self Assessment as a sole trader. The deadline to tell HMRC is 5 October after the end of the tax year in which you started.

The dates

The tax year runs from 6 April to 5 April. For each one:

31 October: the deadline for a paper tax return.
31 January: the deadline for an online tax return, and for paying the tax you owe.
31 July: the second payment on account, if you make them.

Payments on account

These catch many new locums out. As well as settling last year's bill, HMRC asks for payments towards the current year, in two instalments due by 31 January and 31 July. Each is half of the tax you owed last year.

You do not have to make them if last year's bill was under £1,000, or if more than 80% of the tax you owed was already collected at source. Your first January as a locum is usually the expensive one, because it includes both.

Example: If last year's bill was £6,000

31 January: £6,000 for last year, plus £3,000 as the first payment on account. £9,000 in all
31 July: £3,000 as the second payment on account
The following 31 January: This year's bill, less the £6,000 already paid, plus the next first payment on account

Round numbers to show how the dates work. Your own figures will differ.

If you are late

A late return brings an initial £100 penalty, and it grows the longer the return is outstanding: daily penalties after 3 months, then further charges at 6 and 12 months. Late payment is charged separately. Sending the return well before January costs nothing and tells you the figure early.

What to keep

Every session: the date, the workplace and the fee.
Every invoice you send, and when it was paid.
Every business expense, with its receipt.
Your business mileage: the date, where you went and the miles.

You must keep your records for at least 5 years after the 31 January deadline for that tax year. Records kept as you go also meet what Making Tax Digital asks for as your income grows.

Your first year

Your first return covers from the day you started to the following 5 April, even if that is only a few months. Nothing is paid during that first year, which is why the first January comes as a surprise.

Setting money aside

Because nothing is deducted from your fees, the money for the bill has to come from you. Many locums move a share of every payment into a separate account as it arrives. What share is right depends on your income, so ask an accountant early.

If your income drops

Payments on account are based on last year. If you know this year will be lower, you can ask HMRC to reduce them, online or by post. If you reduce them too far, interest is charged on the shortfall.

Sending it early

The return can be sent any time after 5 April. Sending it in the summer does not bring the payment date forward. It only means you know the figure months ahead.

Where Locbase fits

Locbase is where those records are made: sessions, invoices, payments, mileage and expenses with their receipts, by tax year. At the end of the year it exports them in one file for you or your accountant. It does not file your return and it does not work out your tax.

Questions

When is the Self Assessment deadline?

31 January after the end of the tax year for an online return and for payment, and 31 October for a paper return.

Does Locbase do my tax return?

No. Locbase keeps and exports the records your return is built from. You or your accountant send the return to HMRC.

What are payments on account?

Advance payments towards the current year's bill, due by 31 January and 31 July. Each is half of the tax you owed last year.

Can I send my tax return before January?

Yes, any time after the tax year ends on 5 April. The payment is still due by 31 January.