HMRC Self Assessment 2025–26: Who Needs to File, Deadlines, Registration and How to Submit Online

Updated October 24, 2026. HMRC Self Assessment is the process used to report income that has not been fully taxed through PAYE. For the 2025–26 tax year, the return covers income and gains from April 6, 2025 to April 5, 2026. The practical priority is to identify whether you need a return, register or reactivate the correct account, gather records, and keep filing and payment deadlines separate.

This guide is written for individuals preparing their own return. It explains the standard UK route, but your HMRC notice, tax position, residence, partnership status, or type of income can change what you need to do. Use the official GOV.UK links in this article when a rule or deadline matters.

Self Assessment 2025–26: the dates at a glance

The dates below are the standard dates for the 2025–26 tax year. “HMRC receives” matters for a paper return; for an online return, make sure the service confirms that the submission is complete rather than leaving it as a saved draft.

For the current official dates, check HMRC’s Self Assessment deadlines guide. If you register after October 5, 2026, HMRC may give you a different filing deadline in your notice, but the payment deadline can still be January 31, 2027.

What HMRC Self Assessment is—and what it is not

PAYE normally collects Income Tax from employment or pension income before you receive it. Self Assessment is used when HMRC needs you to report income, gains, or other details that are not fully dealt with through PAYE. HMRC then uses the information in the return to calculate what you owe, whether you have overpaid, and whether payments on account are due.

Self Assessment is not a separate bank account and it is not the same thing as a Government Gateway or GOV.UK One Login identity. Registration tells HMRC that you need to complete a return; the sign-in method is how you access an online service. Keep those two decisions separate so you do not register again unnecessarily.

Who normally has to send a tax return?

According to HMRC’s current “who must send a tax return” guidance, you normally need to send one if any of the following applied during the last tax year:

• You were a sole trader and your gross trading income was more than £1,000 before allowable expenses.
• You were a partner in a business partnership.
• You had Capital Gains Tax to pay after selling or disposing of an asset that increased in value.
• You had to pay the High Income Child Benefit Charge and did not pay it through PAYE.
• You were an off-payroll worker who is repaying a student or postgraduate loan.
• You received untaxed income such as rent, tips, commission, savings interest, dividends, foreign income, or other taxable UK income.

You can also choose to file in some situations, for example to prove that you are self-employed, pay voluntary National Insurance contributions, or claim certain tax reliefs. The gross-income test is important: do not subtract expenses before checking whether your trading income passed the £1,000 threshold.

If you are unsure, use HMRC’s check if you need to send a Self Assessment tax return service. It is safer than relying on a generic income threshold from an old article, because the answer depends on the type of income and your circumstances.

First-time registration, reactivation, and the UTR

There are two different situations that are often mixed up:

1. If you have never registered for Self Assessment but now need to file, you must register with HMRC.
2. If you were registered before but did not send a return last year, HMRC may require you to reactivate the account rather than create a second registration.

Start with HMRC’s registration guidance. A first-time filer needs a Unique Taxpayer Reference (UTR) before completing the return. Keep the UTR private and do not send it to anyone who contacts you unexpectedly.

HMRC announced an improved registration service in September 2026. For eligible individual customers using a Personal Tax Account, the service includes pre-populated information, save-and-return support, a confirmation message, and the possibility of seeing the UTR in the online account within 72 hours. That is an improvement to the service, not a guarantee that every case will be completed on the same timetable. Agents continue to use their own registration process.

If your account was already registered, check whether you need to reactivate it. Filing under a new or incorrect registration can delay the return or create avoidable confusion. Also remember that changing from Government Gateway to another sign-in route does not by itself mean you need a new Self Assessment registration.

What to gather before opening the return

Do not start by opening every section of the online form. First make a short evidence folder for the tax year from April 6, 2025 to April 5, 2026.

HMRC says records can be kept on paper, digitally, or in bookkeeping software, but they must be accurate, complete, and readable. You usually do not attach routine receipts to an online return unless HMRC asks for them. Keep the supporting records in case HMRC checks the figures later.

Practical improvement: make a “source” column in your own spreadsheet for each total. A total linked to a bank statement, invoice range, or platform report is much easier to check than a single unexplained number copied into the form.

Paper or online: which filing route should you use?

For most individual filers, the online service is the simpler route because it calculates totals as you go, lets you save progress, and provides a submission confirmation. Paper can still be appropriate when HMRC or your circumstances require a form, but the earlier deadline and delivery risk need to be taken seriously.

The ordinary online service cannot be used for every type of return. HMRC lists partnerships, trusts or estates, some non-resident cases, multiple chargeable-event gains, trust income, Lloyd’s underwriters, and religious ministers among cases that may need commercial software or other forms. Check the official online filing service before relying on a generic tutorial.

How to file Self Assessment online

1. Start from the official GOV.UK service

Use the GOV.UK page for filing your Self Assessment tax return online. Avoid sponsored search ads, links in unexpected messages, and lookalike domains. The official service lets you view previous returns, check details, see what you owe, print your tax calculation, and save your progress.

2. Confirm the tax year and your UTR

Before entering figures, confirm that the return is for 2025–26 and that the account shows the correct UTR. A calendar-year total from January to December is not automatically the same as the UK tax year. If you changed jobs, started trading, moved property, or received foreign income, check the dates rather than copying a prior return.

3. Complete the sections that apply to you

Use the records you gathered. Enter income in the correct category, report expenses or reliefs only where the rules allow them, and keep a note explaining unusual totals. If you have PAYE income, check that it is not being entered twice: once from information already held by HMRC and again from a P60 or P45.

4. Review the calculation before submitting

The calculation is a useful warning signal, not a replacement for checking your entries. Compare the result with your own estimate and look for:

• a missing source of income;
• a figure entered in the wrong tax year;
• a zero accidentally entered where a figure was expected;
• an expense included twice;
• a capital gain treated as ordinary income or left out;
• a payment on account that you were not expecting.

If the result is very different from your estimate, pause and trace the difference before submitting. A larger bill can be correct, but it should be explainable.

5. Submit, save the confirmation, and then pay

Press the final submit control only after reviewing the declaration. Save or print the confirmation reference and the final calculation. A saved draft is not a submitted return. Filing and paying are separate steps: the return tells HMRC what happened, while the payment clears the amount due.

What if you do not know the final profit yet?

HMRC allows provisional figures in situations where you cannot know the final figure by the filing deadline. For example, an accounting period or valuation may still be incomplete. You must identify that provisional figure in the return, keep the reason in your records, and update the return when the final information is available.

The official guidance says you normally have 12 months from the Self Assessment deadline to amend the return. If the final numbers increase the tax due, interest can apply from the original payment date. Do not quietly replace an estimate in your spreadsheet without recording what changed and why.

How much do you pay, and when?

The main payment deadline for the 2025–26 return is January 31, 2027. If payments on account apply, that date can include the balancing payment for 2025–26 plus the first advance payment toward the next tax year. A second payment on account is normally due on July 31, 2027.

You can use HMRC’s Self Assessment payment guide to choose a payment method and check how long it takes. Do not leave a bank transfer or new Direct Debit until the last moment, especially around a weekend or bank holiday.

Can HMRC collect the bill through your PAYE tax code?

Some people can ask HMRC to collect an eligible Self Assessment bill through PAYE. The current official conditions include owing less than £3,000, already paying tax through PAYE, and filing the online return by December 30, 2026. HMRC also applies other eligibility limits, including how much PAYE income is available and how the deduction would affect your tax.

Read the full pay through your tax code guidance before choosing this option. If you miss the December 30 deadline, that does not extend the normal January 31 payment deadline; you will need to use another payment method.

Self Assessment penalties: filing and payment are separate clocks

The penalty risk is easier to understand when you separate a late return from a late payment.

These are the standard rules in HMRC’s penalties guide; reasonable-excuse cases and appeals can change the outcome. If you cannot pay on time, file the return anyway, pay what you can, and use HMRC’s payment-help guidance rather than ignoring the notice.

A short pre-submission audit that catches common mistakes

Use this check immediately before the final submission:

1. The tax year is 2025–26, covering April 6, 2025 to April 5, 2026.
2. Your UTR and National Insurance number belong to the account you are using.
3. Gross trading income was checked before expenses.
4. PAYE income, pension income, savings interest, dividends, rent, foreign income, and gains were each considered.
5. No income or expense total was copied twice.
6. Any provisional figure is clearly identified and supported by a note.
7. The calculation is explainable against your own records.
8. You know the separate filing and payment deadlines.
9. You saved the final submission confirmation.
10. You have a plan for the payment, including any payment-on-account amount.

This list is deliberately short: it is a final error check, not a substitute for the sections that apply to your tax position.

Be careful with HMRC impersonation scams

The Self Assessment deadline creates a predictable wave of fake refund, penalty, and payment messages. Use GOV.UK by typing the address yourself or using the official links above. HMRC’s guidance says suspicious messages may be unexpected, threatening, urgent, or ask for personal or payment information.

Do not share your HMRC sign-in details, UTR, bank information, or security codes because a text message or caller asks for them. You can read HMRC’s current scam-identification guidance and report suspicious contact through the official service.

Official sources checked for this update

• Self Assessment overview
• Who must send a tax return
• Registering for Self Assessment
• File online
• Deadlines
• Penalties
• Pay your tax bill
• HMRC deadline reminder for 2025–26
• HMRC announcement about the improved registration service

Rules and dates in this guide were checked on October 24, 2026. Individual notices and tax circumstances can change the required route, so use the linked HMRC guidance when making a filing or payment decision.