Who needs to do a Self Assessment tax return? A practice guide
Written by the Mipp team
Published: 19 October 2026 | Last checked against GOV.UK: 19 October 2026 | Accurate as of October 2026
Someone needs to do a Self Assessment tax return if they meet one of HMRC's criteria for the tax year, for example self-employment income over £1,000, a partnership share, or Capital Gains Tax to pay. They also need to do one, whatever their income, if HMRC has sent them a notice to file. That second rule is the one that catches practices out. A client can fall outside every criterion and still owe HMRC a return until the notice is withdrawn.
This guide is for UK practices reviewing which clients need a 2025/26 return (the tax year 6 April 2025 to 5 April 2026, due online by 31 January 2027). It covers the GOV.UK criteria, what a notice to file means, and what to do for clients who no longer need to file. Sources were checked on GOV.UK on 19 October 2026. It is a summary, not tax advice for any individual client.
Who must send a tax return
GOV.UK says a person must send a tax return if, in the last tax year, any of these applied:
- they were self-employed as a sole trader and earned more than £1,000, before taking off anything they can claim tax relief on
- they were a partner in a business partnership
- they had to pay Capital Gains Tax on something they sold or disposed of
- they had to pay the High Income Child Benefit Charge and do not pay it through PAYE
- they are an off-payroll worker repaying a student or postgraduate loan
GOV.UK adds that a person may also need to send a return if they have untaxed income, such as:
- rent from property or land
- tips and commission
- savings interest
- dividends, including investments
- foreign income
- any taxable UK income, if they are not UK resident
Some people also choose to file, for example to prove self-employment for Tax-Free Childcare or Maternity Allowance, to pay voluntary National Insurance, or to claim relief on maintenance payments.
If a client meets the criteria but has never filed, or did not need to file for 2024/25, they had to tell HMRC by 5 October 2026 by registering for Self Assessment. Anyone who registers after that date gets a letter or email from HMRC with a filing deadline 3 months from its date, and must still pay by 31 January 2027. Our Self Assessment season plan covers late joiners week by week.
The notice to file: why "HMRC asked" beats the criteria
GOV.UK puts it plainly: "You must send a return if HMRC asks you to." The request is called a notice to file. It is given under section 8 of the Taxes Management Act 1970, and HMRC's legal framework manual says every notice to file requires a return.
The filing dates follow the notice:
| When the notice is given | Paper return due | Online return due |
|---|---|---|
| By 31 July after the tax year | 31 October | 31 January |
| 1 August to 31 October after the tax year | 3 months from the notice | 31 January |
| After 31 October after the tax year | 3 months from the notice | 3 months from the notice |
For 2025/26 that means 31 October 2026 for paper and 31 January 2027 online, for anyone whose notice was given by 31 July 2026.
If a notice to file is outstanding and no return arrives, late filing penalties apply even if no tax is due: £100 straight away, then £10 a day after 3 months (up to £900), then further penalties at 6 and 12 months of 5% of the tax due or £300, whichever is greater. So "they don't really need to file" is not a safe reason to leave a client's return open. Either file it, or get the notice withdrawn.
Where HMRC draws the line
The public guide uses words like "may need to". HMRC's own Self Assessment Manual, which its staff use to decide whether someone needs a Self Assessment record, is more specific. As updated on 9 September 2026, it says:
| Situation | HMRC's manual criterion |
|---|---|
| Income from letting property or land | Gross over £10,000, or net over £2,500 |
| Savings and investment income | £10,000 or more before tax |
| Dividend income | £10,000 or more before tax |
| Other untaxed income | £2,500 or more |
| Expenses or professional subscriptions claimed through the tax code | More than £2,500 |
| Self-employment or a partnership share | Always (except trading income covered by the £1,000 trading allowance) |
| Property income covered by the £1,000 property income allowance | Not usually |
| High Income Child Benefit Charge, 2024/25 onwards | Only if the person chooses not to pay it through PAYE |
The income threshold has gone. Many clients still assume that a high PAYE salary on its own means a return. HMRC's manual says the total income criterion was more than £100,000 for 2017/18 to 2022/23 and £150,000 for 2023/24, and "for 24/25 onwards this criteria does not apply". A PAYE-only client on a high salary may not need a 2025/26 return, unless another criterion applies or HMRC has already sent a notice to file.
Below these levels, HMRC usually collects the tax through the client's tax code instead. That is why the manual matters more than the public guide when you are deciding what to say to a borderline client.
Clients who no longer need to file
Every practice has a few: the landlord who sold the flat, the sole trader who took a job, the parent whose Child Benefit charge now goes through PAYE. GOV.UK gives the same examples and says the taxpayer must tell HMRC "as soon as possible", because HMRC needs time to review the request before 31 January.
How to tell HMRC depends on who is asking:
- The client can use HMRC's online service to say they no longer need to send a return, or do not need to send one for a previous year. They can also phone or write.
- An agent cannot use the online service. GOV.UK says agents should phone or write to HMRC to tell them a client no longer needs to send a return. HMRC's manual confirms it accepts an agent's request as long as the client has authorised the agent.
What HMRC's manuals say happens next:
- HMRC can withdraw the notice if the client no longer meets the Self Assessment criteria for that year.
- If it does, any penalties for failing to file that return are cancelled.
- It cannot withdraw the notice once a return has been received, or if a determination is in place.
- The request must be made within 2 years from the end of the tax year, or a period HMRC agrees.
- HMRC will tell the client whether a return is still needed. Until it does, treat the return as due.
Keep a note of when you phoned or wrote, and what HMRC said. If HMRC later confirms a return is still needed, the original deadline still applies.
Recording "no return this year" in Mipp
Mipp schedules a Self Assessment return for every client with the Self Assessment box ticked on their profile, one row per tax year, due 31 January after the tax year ends. That is right for most clients. For the few whose notice has been withdrawn, or who never had one and don't meet the criteria this year, you need a way to say "not this year" without deleting the client or pretending the return was filed.
That is what Not required does.
- In the Compliance view, find the client's Self Assessment return for the tax year, for example 2025/26.
- Click Not required next to the stage menu. Mipp confirms "Marked not required for this tax year."
- To do several at once, select the rows and choose Not required from Set stage. Only Self Assessment returns change. Any VAT or payroll rows you selected stay as they were.
What changes, and what doesn't:
- The return leaves the Overdue, Due this week and Due this month counters, the progress charts and your calendar feed, so it stops looking like work you owe.
- It is not marked Submitted. It sits in its own grey Not required group, and the status filter can show just those rows, so you can see at a glance who you agreed has no return this year.
- Any task linked to that return is archived.
- It applies to that tax year only. Mipp still schedules the client's next return, for example 2026/27 due 31 January 2028, so a client who starts letting property again isn't missed.
- Undo opens it again ("Self Assessment is open again.") and moves the linked task back to To do. Use it if HMRC replies that a return is still needed.
Not required is only available on Self Assessment returns. For other deadlines that don't apply, Mipp has a separate Not applicable action.
If a client has stopped needing returns for good, untick Self Assessment on their profile so Mipp stops scheduling new years, and mark any open return row Not required.
Mipp does not decide whether a client needs to file, and it does not contact HMRC for you. It records the decision you have made, next to the rest of your HMRC deadlines. As with every date Mipp shows, deadlines are calculated from the details you enter using standard UK rules, so check them against HMRC. For clients who are filing, our reminder letter templates cover the records requests, and the Making Tax Digital deadlines guide covers clients moving to quarterly updates. To see how this fits the rest of the practice's workload, see practice management software for accountants.
Frequently asked questions
Who needs to do a Self Assessment tax return?
Anyone who, in the last tax year, was a sole trader earning more than £1,000, a partner in a partnership, owed Capital Gains Tax, had to pay the High Income Child Benefit Charge outside PAYE, or was an off-payroll worker repaying a student loan. People with untaxed income such as rent, dividends or foreign income may also need to. Anyone HMRC has sent a notice to file must send a return.
Do I need to do a tax return if HMRC hasn't asked me?
If you meet one of the criteria and have not filed before, or did not need to file for 2024/25, you must tell HMRC by registering for Self Assessment by 5 October after the tax year. If you register later, HMRC gives you a filing deadline 3 months from its letter or email, but the tax is still due by 31 January.
Do I have to file if HMRC sent a notice to file but I have no tax to pay?
Yes, unless HMRC withdraws the notice. A notice to file requires a return, and late filing penalties can apply even when no tax is due. If you no longer meet the criteria, ask HMRC to withdraw it as soon as possible.
How does an accountant tell HMRC a client no longer needs to send a return?
Agents cannot use HMRC's online service for this. GOV.UK says an agent should phone or write to HMRC. HMRC accepts the request if the client has authorised the agent, and will tell the client whether a return is still needed.
Is there still a £150,000 income threshold for Self Assessment?
No. HMRC's Self Assessment Manual says the total income criterion was £150,000 for 2023/24 and does not apply from 2024/25 onwards. A PAYE-only client may still need a return for another reason, or because HMRC has sent a notice to file.
Track every client's return in Mipp
Mark the clients who don't need a return this year, keep next year's return in view, and see the rest of your Self Assessment list by stage. Import your client list from a CSV file, with a yes or no column for Self Assessment, and Mipp schedules each client's filing deadlines from the details you include. Start a 14-day free trial. You add a card to start, and nothing is charged for 14 days. Cancel anytime. See pricing for plans.
Sources
All checked on 19 October 2026. Accurate as of October 2026.
- GOV.UK, Self Assessment tax returns: Who must send a tax return; Deadlines; Penalties; If you no longer need to send a tax return (guide last updated 5 November 2024). https://www.gov.uk/self-assessment-tax-returns
- GOV.UK, Check if you need to send a Self Assessment tax return (updated 17 December 2024). https://www.gov.uk/check-if-you-need-tax-return
- GOV.UK, HMRC internal manual, Self Assessment Legal Framework SALF203: Personal Tax Returns (updated 10 April 2019). https://www.gov.uk/hmrc-internal-manuals/self-assessment-legal-framework/salf203
- GOV.UK, HMRC internal manual, Self Assessment Manual SAM100050: criteria for a PAYE / SA record (updated 9 September 2026). https://www.gov.uk/hmrc-internal-manuals/self-assessment-manual/sam100050
- GOV.UK, HMRC internal manual, Self Assessment Manual SAM100060: criteria for an SA record (updated 9 September 2026). https://www.gov.uk/hmrc-internal-manuals/self-assessment-manual/sam100060
- GOV.UK, HMRC internal manual, Self Assessment Manual SAM120115: withdrawing a notice to file (updated 1 July 2019). https://www.gov.uk/hmrc-internal-manuals/self-assessment-manual/sam120115
- GOV.UK, HMRC internal manual, Compliance Handbook CH61700: withdrawal of obligation (updated 15 January 2016). https://www.gov.uk/hmrc-internal-manuals/compliance-handbook/ch61700