The short answer
How to register for UK Self Assessment for 2025/26 income, who needs to register, the 5 October deadline, UTR timing and what to do next.
If you need to file a UK Self Assessment return for the 2025/26 tax year, you may need to register with HMRC before filing. HMRC’s improved individual registration service launched on 9 September 2026 and provides a more streamlined route through a Personal Tax Account.
For a person who first needs to notify HMRC for 2025/26, the usual notification deadline is 5 October 2026. The online tax-return and payment deadline is generally 31 January 2027, but you must register first and receive a Unique Taxpayer Reference (UTR) before starting the return.
Use the Salary Calculator for an indicative PAYE comparison only. It cannot decide whether Self Assessment registration is required or submit a return.
5 October 2026 notification date
Register before filing
New UTR delivery flow
Who may need to register?
HMRC’s current “who must send a tax return” guidance includes people who:
- were self-employed as a sole trader and earned more than £1,000 gross in the tax year;
- were a partner in a business partnership;
- had Capital Gains Tax to pay after disposing of an asset;
- had a High Income Child Benefit Charge that was not paid through PAYE; or
- received untaxed income, such as property income, tips, commission, savings interest, dividends or foreign income.
The list is not a substitute for HMRC’s online checker. Your wider income, reliefs, tax already collected and filing history can change the required route.
The £1,000 trading allowance also needs careful handling. Gross trading income below £1,000 can fall within the trading allowance, but a person may still choose or need to file for another reason. The allowance does not erase unrelated property, dividend, foreign-income or Capital Gains Tax obligations.
The 5 October 2026 deadline
If you need to complete a return for 2025/26 and have not filed Self Assessment before, HMRC says you must tell it by 5 October 2026. The same notification rule can apply where you were registered before but did not need to send a return for 2024/25 and now need one for 2025/26.
The date is a registration or notification deadline, not the final online payment date. For 2025/26, HMRC states that the online return and payment deadline is 31 January 2027. Leave time for identity checks, the UTR, records and any payment-on-account calculation.
How the individual online registration works
HMRC’s improved service is for individual customers with a Personal Tax Account. The announced improvements include:
- sign in or create a Personal Tax Account using the available Government Gateway or GOV.UK One Login route;
- use HMRC’s eligibility guidance or online checker before registering;
- provide the requested income and personal details;
- complete the registration and keep the confirmation email or text;
- find the UTR in the online account; and
- use the UTR to set up and submit the Self Assessment return.
HMRC says forms can be pre-populated, registration can be saved and resumed, and the UTR can appear in the online account within 72 hours for users of the new service. This is an expected service target, not a guarantee that every case will be completed in that time.
What if you are already registered?
Do not create a duplicate registration simply because a new tax year has started. Check the account and filing history first. HMRC says people who were already registered but did not submit a return for 2024/25 may need to reactivate the account if they need to file for 2025/26.
If your circumstances have changed and you no longer need to file, tell HMRC as soon as possible. Until HMRC confirms that a return is no longer expected, continue to meet the relevant filing and payment obligations rather than assuming the record has closed.
Individuals, agents and businesses use different routes
The improved online service is for individual customers. HMRC says agents continue to use existing processes, including forms CWF1 or SA1, where appropriate. A partnership, limited company or employer may also have a separate registration and return contract.
Do not use an individual’s UTR or Personal Tax Account as a substitute for a partnership or company registration. Confirm the taxpayer and legal entity before entering details or authorising an agent.
What to prepare before registering
Have the following ready:
- National Insurance number and identity details;
- the date self-employment, partnership or other untaxed income started;
- gross trading or property income and any related records;
- details of employment, pension, savings, dividends or foreign income;
- previous UTR or Self Assessment references, if already registered; and
- bank, expense, pension and charitable-giving records for the return.
Registration does not calculate the final tax bill. It only establishes the account and filing route. Keep records that support the amounts later entered on the return.
Decide what triggered the registration
Write down the reason you believe a return is required before opening the registration service. It might be sole-trader income, partnership income, property income, foreign income, dividends, a High Income Child Benefit Charge, a capital gain or another HMRC instruction. The trigger determines which records and return sections may be relevant. A person can have more than one trigger, so registering for one reason does not remove the need to report another source of income or gain.
Separate gross receipts from taxable profit. The trading allowance is based on gross trading income, while property, dividends, savings interest and foreign income follow different rules. A bank statement showing money received is not a substitute for a schedule of the source, date, expenses and tax already deducted. Prepare the records before registering so that the later return does not rely on a rough total created from memory.
Registration after a change in circumstances
A new trade, property letting, directorship, investment disposal or change in family income can create a registration question during the year. Keep the start date and the date you first became aware that a return might be required. If the source stops, do not simply ignore the account: tell HMRC that the circumstances changed and ask whether a return is still expected for the relevant year.
If you move from sole trader to partnership, incorporate a business, appoint an agent or become non-UK resident, check the entity and residence rules before using the individual route. The same person can have a personal return and be connected to another registration, but a personal UTR is not a company or partnership identifier. Save correspondence showing which registration HMRC accepted.
What happens after the UTR arrives
Finding a UTR is only the start of the filing process. Confirm the tax year, accounting period, sources of income, allowable expenses, pension contributions, charitable giving, student loan information and payments already made through PAYE. Check whether the return will create a payment on account for the next tax year. The amount due on 31 January can therefore be more than the balance for the year just ended.
Keep a dated record of the registration confirmation, UTR, online account messages and any HMRC request for additional information. If the UTR does not arrive within HMRC's stated service route or the account shows an error, contact HMRC with the confirmation rather than registering again. Duplicate registrations can create administrative confusion and do not remove the original notification deadline.
Stopping Self Assessment safely
When a trade ends or untaxed income falls away, check whether a final return is needed for the period in which the activity existed. File that return, pay any liability and then tell HMRC if you no longer need to file. Keep records for the required period and retain the closure confirmation. Stopping a source of income does not automatically cancel a return that HMRC has already issued.
If HMRC sends a notice to file after you believe the account should be closed, respond through the official route and explain the facts. Do not assume that a nil return is always the right answer or that ignoring the notice will close the account. The filing status, penalties and appeal route depend on the notice and the tax year.
Keep a short filing trail showing the date you checked eligibility, the date you registered, the UTR confirmation, the tax year covered and the date you filed. This makes it easier to explain a late registration or correct a duplicate record. Save the final submission receipt and payment reference with the underlying income schedule, not only in an email inbox.
Registration is not the same as payment
After registration, work out the return carefully and check whether the 31 January payment includes a payment on account for the next year. The amount can include Income Tax, Class 4 National Insurance and other liabilities depending on the income and circumstances.
PAYE deductions do not automatically settle tax on a separate trade, property business or investment income. Conversely, not every untaxed receipt means that an individual must complete the same Self Assessment sections. Use HMRC’s current checker and return guidance for the exact route.
Do not wait for the UTR before checking the deadline
The UTR is needed before filing, but waiting for it does not move the 5 October registration deadline. Register early, keep the confirmation and contact HMRC if the account or UTR is delayed.
Practical registration checklist
- Check whether you need to send a return for 2025/26.
- Note the 5 October 2026 first-notification deadline where it applies.
- Register through the individual online service or the correct agent/entity route.
- Save the confirmation and locate the UTR.
- Gather records and complete the relevant return sections.
- File and pay by 31 January 2027 if using the online route, unless a different HMRC deadline applies.
- Tell HMRC if you no longer need to file, and retain confirmation.
Save the registration trail
After submitting registration, save the confirmation screen, date, reason for registration, expected income source and any HMRC correspondence. Check that the name, address, National Insurance number and business details match the records you will use on the return. A UTR arriving later does not itself prove that every obligation has been satisfied; record the tax year, filing deadline and payment dates separately. If the activity stops, changes from sole trade to company, or becomes fully taxed through PAYE, ask HMRC what notice or return action is required and retain the confirmation.
Before the first return, build a simple evidence folder for invoices, bank records, expenses, pension contributions, foreign income and tax already deducted. Registration is the beginning of the filing process, not a substitute for deciding which supplementary pages and records apply.
Frequently Asked Questions
When do I need to register for Self Assessment for 2025/26?
Can I file a Self Assessment return before I get my UTR?
How long does the new UTR service take?
Do agents use the new online service?
What is the online Self Assessment deadline for 2025/26?
Do I need to register if my self-employed income is £1,000 or less?
Can property, dividend or foreign income require Self Assessment?
What if I was registered for Self Assessment before?
Is 5 October 2026 the same as the tax-payment deadline?
What should I do if I no longer need to file a tax return?
Related reading: the Self Assessment deadlines guide, the Self Assessment filing guide and the Side Hustle Tax guide.
Official sources
Related Guides
Sole Trader vs Limited Company 2026/27 — Tax & Pay
Sole trader vs limited company in 2026/27: income tax, National Insurance, Corporation Tax, dividends, IR35 and extraction choices.
Trading Allowance 2026/27 — £1,000 Limit & Rules
The £1,000 trading allowance for 2026/27: who qualifies, Self Assessment registration, choosing the allowance over expenses and property-income interactions.
Sole Trader Expenses 2026/27 — Allowable Costs & Claims
Sole trader expenses in 2026/27: wholly-and-exclusively tests, simplified home-office and mileage rates, capital costs and Self Assessment claims.
Review notes and assumptions
Reviewed
2026-09-20
Assumptions
- This guide covers registration for an individual filing a Self Assessment return for the 2025/26 tax year in the 2026/27 filing cycle; it does not replace HMRC’s personalised eligibility check.
- The 5 October 2026 date applies to a person who first needs to notify HMRC for the 2025/26 tax year, subject to the actual facts and HMRC rules.
- Agents, partnerships and limited companies can have different registration processes and are not covered by the individual online flow described here.