If you need to complete a Self Assessment tax return for 2025/26, the tax year that ended on 5 April 2026, the date to work to is 31 January 2027. Your return must be filed online, and any tax you owe paid, by 11:59pm that day.
The figures in this post were checked on GOV.UK on 23 October 2026. The Budget on 28 October 2026 may change some of them, and we will review this post against GOV.UK after it.
On this page:
- The deadlines for 2025/26
- If you still need to register
- What to have ready before you file
- Payments on account
- What filing or paying late costs
- Does this year’s return put you into Making Tax Digital?
- How we can help
When is the Self Assessment deadline for 2025/26?
GOV.UK sets out these dates for the 2025/26 return:
- 30 December 2026: online returns where you want the tax collected through your PAYE tax code.
- 31 January 2027: online returns, by 11:59pm; payment of the tax you owe for 2025/26; and the first payment on account towards your 2026/27 tax, if you have to make them.
- 31 July 2027: the second payment on account towards your 2026/27 tax, if you have to make them.
Collection through your tax code needs three things: you owe less than £3,000, you already pay tax through PAYE, and you file online by 30 December 2026. You cannot make a part payment to get under £3,000. HMRC will also turn it down if you do not have enough PAYE income, or if it would mean paying more than half your PAYE income in tax, or more than twice as much tax as you normally do.
If you still need to register for Self Assessment
If 2025/26 is your first year, you were due to tell HMRC by 5 October 2026. That date has passed, and GOV.UK says you could get a penalty for telling HMRC after it, so it is better to register now than to wait until January. You can register for Self Assessment on GOV.UK, or we can register you as your agent.
If you register now, GOV.UK says HMRC will write or email with a filing deadline three months from the date of that letter. The tax you owe for 2025/26 is still due by 31 January 2027: the later filing date does not move the payment date.
You will usually need to file for 2025/26 if any of these applied:
- You were self-employed as a sole trader and earned more than £1,000, measured before deducting anything you can claim tax relief on.
- You were a partner in a business partnership.
- You had Capital Gains Tax to pay.
- You had to pay the High Income Child Benefit Charge and did not pay it through PAYE.
- You had rental income of more than £2,500 after allowable expenses, or more than £10,000 before them.
You may also need to file if you had untaxed income, such as savings interest, dividends, tips or commission, or foreign income, or if you are an off-payroll worker repaying a student or postgraduate loan. On rental income, the first £1,000 of property income is covered by the property allowance, and between £1,000 and £2,500 after expenses GOV.UK asks you to contact HMRC rather than file.
If you registered in an earlier year but did not have to file last year, your record may need reactivating first, or the return may be delayed. HMRC publishes no fixed timescale for issuing a Unique Taxpayer Reference, the ten-digit number, often shortened to UTR, that identifies you for Self Assessment, so check its guide to when you can expect a reply.
What you need to have ready before you file
Missing records are a common cause of delay in January. It helps to have:
- Income and expenses for any self-employment or trade.
- Rental income and allowable expenses for each property, which our accountants for landlords can work through with you.
- Bank and building society interest. The Personal Savings Allowance is £1,000 for basic rate taxpayers, £500 for higher rate taxpayers and nothing for additional rate taxpayers. If your other taxable income, not counting savings interest or dividends, was under £17,570, you may also qualify for the starting rate for savings, which can cover up to £5,000 of interest.
- Dividends received, including from your own company. The dividend allowance is £500 a year.
- Details of anything you sold or disposed of that had gone up in value. For 2025/26 the Capital Gains Tax annual exempt amount is £3,000 for individuals.
- Child Benefit received, if the higher earner in your household had adjusted net income over £60,000 for 2025/26. All of it is repaid once that income is over £80,000, and it is the higher earner who reports and pays the charge.
Gathering the figures in November or December also leaves time to act on what they show, which is the point of personal tax planning rather than reporting a closed year.
Payments on account: what they are and when they are due
Payments on account are advance payments towards the following year’s tax. The first falls on the same day as the balancing payment for the year just filed, which can make a January bill larger than expected.
- They are due by 11:59pm on 31 January and 31 July.
- Each payment is usually 50% of the previous year’s Self Assessment liability, which is to say half of the tax you owed last year. Capital Gains Tax and student loan repayments are left out of that calculation and fall into the balancing payment instead, so the payments can be less than half of the bill you actually paid.
- You do not have to make them if the tax you owed last year was less than £1,000, or if you paid more than 80% of last year’s tax outside Self Assessment, for example through your tax code.
- The balancing payment is the tax for the year less the payments already made, and it is due by 11:59pm on 31 January the following year.
If your profits or other income have fallen, or more tax has been deducted at source than last year, you can apply to reduce the payments, online or on form SA303. The claim must be made by the 31 January after the end of the tax year the payments are for, so for the payments towards 2026/27 that is 31 January 2028. If the bill then turns out higher than expected, HMRC charges interest on the difference, so it is better to reduce them only to the figure you can support.
What it costs to file or pay late
For 2025/26 returns the late filing penalty is £100 as soon as the deadline is missed. That applies even if you have no tax to pay. After three months it becomes £10 a day, up to £900. At six months it is 5% of the tax due or £300, whichever is greater, and the same again at twelve months.
For 2025/26, paying late is charged separately: 5% of the tax unpaid at 30 days, at six months and at twelve months, plus interest. HMRC’s late payment interest rate was 7.75% as at 23 October 2026, in force since 9 January 2026. It is set as the Bank of England base rate plus 4 percentage points, so it moves when the base rate moves; the GOV.UK page for HMRC interest rates carries the current figure.
If you can file but cannot pay
Filing on time at least stops the filing penalties. Once the return is in, HMRC lets many people spread the cost with a payment plan arranged online, generally where no more than £30,000 is owed, with interest on the balance. HMRC also expects you to have no other tax debts or payment plans, to set the plan up within 60 days of the payment deadline, and to clear it within 12 months. Above £30,000, or outside those conditions, you need to speak to HMRC instead. You can check your eligibility and set up a payment plan on GOV.UK.
If a penalty has been issued, you usually have 30 days from the date of issue to contact HMRC or appeal, and GOV.UK lists what counts as a reasonable excuse.
Does this year’s return put you into Making Tax Digital?
Your 2025/26 return also decides whether you join Making Tax Digital for Income Tax on 6 April 2027. As currently legislated, anyone whose qualifying income for 2025/26 was over £30,000 must use the service from that date unless they are exempt. Qualifying income is your total income from self-employment and property before expenses: it does not include employment income taxed through PAYE, dividends or pensions. The first stage is already running, for income over £50,000 on the 2024/25 return, and a third follows on 6 April 2028 for qualifying income over £20,000.
Three things are commonly misunderstood. It does not replace the tax return, which is still submitted by 31 January. It does not change how or when you pay, so payments on account stay on 31 January and 31 July. And the year before you start is filed in the usual way, under the current penalties.
What does change is the record keeping, the quarterly updates and, from your first year in the service, the penalties. You can check if and when you need to use Making Tax Digital for Income Tax on GOV.UK, and our full guide to Making Tax Digital for Income Tax sets out the records, the software, the quarterly deadlines and the new penalties in detail. Landlords can read how it applies to rental income in our guide to Making Tax Digital for landlords, and we handle it for clients through our Making Tax Digital service.
What we do for Self Assessment clients
3DOM.uk Accountants is based at Second Floor, 61 Hamilton Square, Birkenhead CH41 5AT. We act for clients across the Wirral and elsewhere in the UK, and for clients who use our accountants in Liverpool. On a Self Assessment tax return we register you with HMRC if needed, act as your agent, prepare the return from your records, put the figures to you for approval before anything is submitted, and set out what to pay and when.
Tax returns start from £350 plus VAT, depending on the number of income sources and the state of the records.
If you would like us to take the 2025/26 return on, or to know where you stand before January, you are welcome to book a free, no-obligation consultation.