Guide | All locums
Locum tax return checklist for 31 January 2027
If your self-employed locum income between 6 April 2025 and 5 April 2026 was more than £1,000 before expenses, your 2025/26 Self Assessment return is normally due online by 11:59pm on 31 January 2027, and so is the tax. In your first year, that payment can also include an advance towards the next year's bill.
Below is what to gather, which income belongs in which year, how the January bill is made up, and what a late return costs, with the GOV.UK page behind each rule.
Checked on against the primary sources listed at the end of this page.
Key dates for the 2025/26 tax return
| Date | What happens | Source |
|---|---|---|
| 5 October 2026 | Last day for a first-time filer to register for Self Assessment | GOV.UK, register |
| 31 October 2026 | Paper return deadline | GOV.UK, deadlines |
| 30 December 2026 | File online by now to ask for a bill under £3,000 to be collected through your PAYE tax code, if you have enough PAYE income for HMRC to collect it | GOV.UK, deadlines |
| 31 January 2027 | Online return, the 2025/26 balancing payment and the first payment on account for 2026/27 | GOV.UK, pay your bill |
| 31 July 2027 | Second payment on account for 2026/27 | GOV.UK, payments on account |
The 30 December date matters to locums who also hold a salaried or PAYE post: spreading a bill through the tax code can be easier than finding it in one go in January.
What to gather before you file
- Every payment for self-employed work. Each invoice and the date it was paid, for payments received from 6 April 2025 to 5 April 2026. Sessions, out-of-hours shifts and any other fees you invoiced yourself.
- P60s and P45s for employed work. Salaried posts, bank work and agency shifts paid through PAYE go on the employment pages, not in your business income.
- Business expenses. Registration fees, indemnity, professional memberships, equipment, the business share of your phone, training that keeps your skills current, and accountancy fees for the business, such as preparing your business accounts; fees for personal tax matters are not allowable, so ask your accountant which part of their fee is for the business. GOV.UK's expenses list sets the test: the cost has to be for the business.
- A mileage log. Date, start and end, miles and the reason for each business journey. For 2025/26 the flat rate for a car was 45p a mile for the first 10,000 miles and 25p after that.
- Pension paperwork. For locum GPs, Forms A and B and your contribution figures; your accountant will know where they go. Our guide to NHS pension Forms A and B covers the forms.
- Everything else. Savings interest, dividends, rental income and any student loan plan, because the return covers your whole income, not only the locum work.
- Your UTR and HMRC sign-in. Government Gateway or GOV.UK One Login. If you are still registering, HMRC's online registration service puts the UTR in your online account within 72 hours; a UTR sent by post can take up to 15 days.
Which locum income belongs in 2025/26?
Under the cash basis, the standard method for a sole trader, income counts when the money arrives and expenses when you pay them. An organisation that pays a March 2026 invoice on or after 6 April 2026 puts that income into 2026/27, which surprises people who add up their sessions by date worked. If you use traditional accounting instead, income counts in the period you earn it, normally when you do the work, even if you invoice or are paid later, and the return asks you to say you used it.
A locum who also did agency or salaried work keeps the two apart: the PAYE income goes on the employment pages with the tax already deducted, and only the self-employed fees go in the business pages. Both feed the same tax calculation, which is how the employed work can push locum profit into a higher band.
How big is the January bill in your first year?
Payments on account are advance payments towards the next tax year, due on 31 January and 31 July. Each is normally half of the previous year's income tax and Class 4 National Insurance, after deducting tax paid at source and any underpayment moved into your PAYE tax code; Capital Gains Tax, student loan repayments and Class 2 are left out. You do not make them if that bill was under £1,000 or more than 80% of your tax was collected at source. In your first year nothing has gone in advance, so where payments on account apply, the 31 January payment carries the whole 2025/26 bill plus the first advance towards 2026/27.
| Item | How it is worked out | Amount |
|---|---|---|
| Income tax | (£50,000.00 less the £12,570.00 personal allowance) at 20% | £7,486.00 |
| Class 4 National Insurance | (£50,000.00 less £12,570.00) at 6% | £2,245.80 |
| 2025/26 bill | Income tax plus Class 4 | £9,731.80 |
| First payment on account for 2026/27 | Half of the 2025/26 bill | £4,865.90 |
| Due 31 January 2027 | The bill plus the first payment on account | £14,597.70 |
| Due 31 July 2027 | Second payment on account | £4,865.90 |
Class 2 National Insurance is not added to the bill: with profits of £6,845.00 or more for 2025/26 it is treated as paid, protecting your record, and below that you can choose to pay voluntary contributions. Scottish taxpayers pay different income tax bands, so the income tax line would differ; Class 4 is the same across the UK. If the advance payments look too high because this year's income has fallen, you can ask HMRC to reduce them, but if you reduce them too far you pay interest on the shortfall. GOV.UK also lets you pay towards the bill in instalments before the deadline.
What does a late return cost?
| When | Late return | Late payment |
|---|---|---|
| Day after the deadline | £100, even if no tax is owed | Interest starts |
| 30 days | No change | 5% of 2025/26 tax still unpaid |
| 3 months | £10 a day, up to 90 days (£900) | No change |
| 6 months | 5% of the tax due or £300, whichever is greater | Another 5% |
| 12 months | Another 5% or £300, whichever is greater | Another 5% |
Those are GOV.UK's figures. The late payment penalties apply to 2025/26 tax still unpaid, counted from 31 January 2027; the 2026/27 payment on account due that day carries interest if it is paid late. You can appeal against a penalty if you have a reasonable excuse. If a final figure genuinely cannot be had before the deadline, HMRC accepts a return on time with a reasonable provisional figure, marked and explained, amended as soon as the final figure is known.
After you file
Keep the records for at least 5 years after the 31 January deadline, so the 2025/26 records until at least 31 January 2032. Set aside for the July payment now. And if your qualifying income (self-employment and property income before expenses) was over £50,000 in 2024/25, Making Tax Digital for Income Tax already applies from 6 April 2026 unless you are exempt, with quarterly updates for 2026/27; the threshold falls to £30,000 from April 2027 and £20,000 from April 2028.
You must send a return at all only if you earned more than £1,000 from self-employment in the year before expenses, or another of GOV.UK's reasons applies.
Reference notes | Questions
Frequently asked questions
When is the deadline for a locum tax return?
For the 2025/26 tax year (6 April 2025 to 5 April 2026), the normal deadline for an online return is 11:59pm on 31 January 2027, and the tax you owe is due the same day. The paper deadline is 31 October 2026. If you are new to Self Assessment you should have registered by 5 October 2026. If you register after that, your online filing deadline is the later of 31 January 2027 and 3 months after HMRC sends you notice to file, but the tax is still due by 31 January 2027.
Do I need to file a tax return as a locum?
Yes if you worked as a self-employed sole trader and earned more than £1,000 before expenses in the tax year. Locum work paid through an agency or on a payslip, with tax taken under PAYE, does not on its own need a return, but many locums have both kinds of work and file for the self-employed part.
Which locum income goes on my 2025/26 return?
Under the cash basis, which is the standard method for a sole trader, income counts when you receive the money, not when you worked or invoiced. A session worked in March 2026 and paid on or after 6 April 2026 belongs in 2026/27. Work out your 2025/26 self-employed income from payments received between 6 April 2025 and 5 April 2026.
What is a payment on account, and why is my first bill so big?
Payments on account are advance payments towards the next tax year's bill, due on 31 January and 31 July. Each is normally half of the previous year's income tax and Class 4 National Insurance, after deducting tax paid at source and any underpayment moved into your PAYE tax code; Capital Gains Tax, student loan repayments and Class 2 are left out. You do not make them if that bill was under £1,000 or more than 80% of your tax was collected at source. In your first year nothing has been paid in advance, so where payments on account apply, the 31 January bill is the whole 2025/26 amount plus the first advance towards 2026/27. A locum with £50,000.00 of profit and no other income in England would owe £9,731.80 for 2025/26 and pay £14,597.70 on 31 January 2027.
What happens if I miss 31 January?
A late return gets a £100 penalty straight away, even if no tax is owed. After 3 months HMRC adds £10 a day for up to 90 days, then 5% of the tax due or £300, whichever is greater, at 6 months and again at 12 months. Tax paid late carries interest. 2025/26 tax still unpaid 30 days after 31 January 2027 attracts a 5% penalty, with a further 5% at 6 months and at 12 months; the 2026/27 payment on account due the same day carries interest if it is late. You can appeal against a penalty if you have a reasonable excuse.
Does Making Tax Digital change this return?
No. The 2025/26 return is filed in the usual way. Making Tax Digital for Income Tax brings digital records and quarterly updates for sole traders whose qualifying income (self-employment and property income before expenses) was over £50,000 in 2024/25, from 6 April 2026 unless exempt, so if that is you, the quarterly updates are for 2026/27 and later.
Make next January a download, not a search
Sessional records your sessions, invoices and the date each one was paid, and exports invoices with their payment dates as a CSV on every plan, so reconciling a tax year's cash-basis income starts from one list. On Plus and Pro it also logs expenses and mileage at the HMRC rate for each journey's tax year and calculates a suggested tax reserve as you earn. Basic is free with no card.
Sources
Each source below was read on unless it says otherwise. Rules and rates change: check the source before you rely on a figure, and tell us if something here is out of date.
- GOV.UK, Self Assessment tax returns: deadlines: for 2025/26: register by 5 October 2026, paper return by 31 October 2026, online return and payment by 11:59pm on 31 January 2027, and online by 30 December 2026 to pay through a PAYE tax code
- GOV.UK, register for Self Assessment: that a new filer tells HMRC by 5 October after the end of the tax year (5 October 2026 for 2025/26)
- HMRC, improved online service makes it easier to register for Self Assessment (9 September 2026): that the online registration service issues the UTR in the online account within 72 hours, instead of up to 15 days by post
- GOV.UK, Self Assessment tax returns: who must send a tax return: that a sole trader who earned more than £1,000 before expenses in the tax year must send a return
- GOV.UK, pay your Self Assessment tax bill: that the balancing payment and first payment on account are due by 31 January and the second payment on account by 31 July, and that you can pay in instalments before the deadline
- GOV.UK, understand your Self Assessment tax bill: payments on account: that each payment is half of last year's tax, due by 31 January and 31 July, and the two cases where you do not make them (under £1,000, or more than 80% paid outside Self Assessment)
- GOV.UK, cash basis: that cash basis is the standard way for a sole trader to record income and expenses, counting income when it is received, and that traditional accounting is a choice declared on the return
- GOV.UK, expenses if you're self-employed: that allowable expenses are deducted to work out taxable profit, and that using the £1,000 trading allowance rules out claiming expenses
- GOV.UK, simplified expenses: vehicles: the 2026/27 flat rates per mile (55p then 25p for cars and goods vehicles, 24p for motorcycles), 45p before 6 April 2026, and that once you use flat rates for a vehicle you keep using them
- GOV.UK, self-employed National Insurance rates: that Class 2 is treated as paid at or above the small profits threshold rather than charged, and that Class 4 is paid through Self Assessment at 6% between £12,570 and £50,270 and 2% above
- GOV.UK, Self Assessment tax returns: penalties: late filing penalties (£100, then £10 a day after 3 months up to £900, then 5% or £300 at 6 and 12 months), 5% late payment penalties at 30 days, 6 months and 12 months, plus interest
- GOV.UK, business records if you're self-employed: how long to keep your records: that records are kept for at least 5 years after the 31 January submission deadline of the tax year they relate to
- GOV.UK, check if you're eligible for Making Tax Digital for Income Tax: the thresholds and start dates: over £50,000 in 2024/25 from 6 April 2026, over £30,000 in 2025/26 from 6 April 2027, over £20,000 in 2026/27 from 6 April 2028
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