UK Self-Assessment 2026/27: Deadlines, Penalties, MTD ITSA
UK Self Assessment 2026/27: register by 5 October, file by 31 October (paper) or 31 January (online), payments on account, penalties, interest and MTD.
2026/27 key dates
| Date | What | Detail |
|---|---|---|
| 5 October 2027 | Tell HMRC you need to file | If you need to file a 2026/27 return and have not before (for example you started self-employment or letting), tell HMRC by 5 October 2027. Missing this can lead to a failure-to-notify penalty (FA 2008 Sch 41). |
| 31 October 2027 | Paper return deadline | Paper returns for 2026/27 must reach HMRC by 11:59pm. A late return gets a £100 penalty even if no tax is due. |
| 30 December 2027 | Online deadline to pay through your tax code | If you owe less than £3,000, file online by 30 December (or on paper by 31 October) and you pay PAYE, HMRC can collect it through your 2028/29 tax code (gov.uk). |
| 31 January 2028 | Online return, balancing payment and first payment on account | File the 2026/27 return online, pay the 2026/27 balancing payment, and make the first payment on account for 2027/28 (half of the previous year's Income Tax and Class 4 NI bill). |
| 31 July 2028 | Second payment on account for 2027/28 | The other half of the payments on account for 2027/28. |
| 31 January 2029 | Balancing payment for 2027/28 + first payment on account for 2028/29 | Any difference between the payments on account and the actual 2027/28 liability is settled. |
SA penalty structure
| Trigger | Amount | Authority | Notes |
|---|---|---|---|
| Late filing - day after the deadline | £100 fixed | FA 2009 Sch 55 para 3 | Even if no tax is owed |
| Late filing - 3 months late | £10 a day for up to 90 days (max £900) | FA 2009 Sch 55 para 4 | HMRC must give notice |
| Late filing - 6 months late | Greater of 5% of the tax due or £300 | FA 2009 Sch 55 para 5 | |
| Late filing - 12 months late | Greater of 5% or £300; up to 70% (deliberate) or 100% (deliberate and concealed) of the tax if information is withheld | FA 2009 Sch 55 para 6 | Reduced for disclosure |
| Late payment - 30 days late | 5% of the unpaid tax | FA 2009 Sch 56 para 3 | Not on payments on account |
| Late payment - 6 months late | A further 5% | FA 2009 Sch 56 para 3 | |
| Late payment - 12 months late | A further 5% | FA 2009 Sch 56 para 3 | |
| Inaccurate return | Careless up to 30%, deliberate up to 70%, deliberate and concealed up to 100% of potential lost revenue (higher for offshore matters) | FA 2007 Sch 24 | Reduced for disclosure |
| Failure to notify | Percentage of the tax unpaid, by behaviour | FA 2008 Sch 41 |
These are the current Self Assessment penalties. If you have joined Making Tax Digital for Income Tax, the new points-based late submission penalties and the new late payment penalties apply instead from the tax year you join, and from April 2027 they apply to everyone who submits a personal Self Assessment return (gov.uk).
MTD ITSA phase-in
Making Tax Digital for Income Tax requires sole traders and landlords above a qualifying income threshold to keep digital records and send quarterly updates, then file a tax return by 31 January.
| Required from | Qualifying income over | Measured in |
|---|---|---|
| 6 April 2026 | £50,000 | 2024-25 |
| 6 April 2027 | £30,000 | 2025-26 |
| 6 April 2028 | £20,000 | 2026-27 and later |
Source: The Income Tax (Digital Obligations) Regulations 2026 (SI 2026/336), reg 27. Quarterly updates are due by the 7th of August, November, February and May.
Related guides + calculators
Frequently asked questions
Who must file a Self-Assessment tax return for 2026/27?
Per gov.uk you must send a return if, in the tax year: (a) you were self-employed as a sole trader and earned more than £1,000 before expenses; (b) you were a partner in a business partnership; (c) you had to pay Capital Gains Tax; (d) you had to pay the High Income Child Benefit Charge (adjusted net income over £60,000) and do not pay it through PAYE; or (e) you are an off-payroll worker repaying a student or postgraduate loan. You may also need to file for other untaxed income - rental income, tips and commission, savings interest, dividends, foreign income, or UK income as a non-resident - or to claim some reliefs such as venture capital schemes. You must also file if HMRC sends you a notice to file. Use the gov.uk checker if unsure.
How do Payments on Account (POA) work?
Payments on account are advance payments towards your current year's bill, each usually half of the previous year's Income Tax and Class 4 NI. They are due on 31 January and 31 July. You do not have to make them if last year's Self Assessment bill was less than £1,000, or if more than 80% of the tax you owed was paid outside Self Assessment, for example through your tax code (gov.uk). Capital Gains Tax and student loan repayments are paid with the balancing payment, not through payments on account. Example: a 2026/27 bill of £8,000 means two payments of £4,000 towards 2027/28, on 31 January 2028 and 31 July 2028. If you expect a lower bill you can ask HMRC to reduce them (form SA303); if you reduce them too far, interest is charged on the shortfall.
What is Making Tax Digital for Income Tax Self-Assessment (MTD ITSA)?
Sole traders and landlords with qualifying income above a threshold must keep digital records and send quarterly updates through compatible software, then submit a tax return by 31 January after the tax year. The thresholds are set by The Income Tax (Digital Obligations) Regulations 2026 (SI 2026/336), reg 27: over £50,000 of qualifying income in 2024-25 brings you in from 6 April 2026; over £30,000 of qualifying income in 2025-26 brings you in from 6 April 2027; over £20,000 of qualifying income in 2026-27 and later brings you in from 6 April 2028. Quarterly updates are due by the 7th of August, November, February and May. Penalties: for MTD users, points-based late submission penalties replace the old ones - a £200 penalty at 4 points and for each further missed deadline - but there are no penalties for missing a quarterly update for 2026/27. New late payment penalties also apply (see the next answers) (gov.uk).
How do I appeal a Self-Assessment penalty?
You usually have 30 days from the date of the penalty notice to appeal to HMRC (gov.uk). If HMRC does not change its decision, it will offer a review; you then have 30 days to accept the review or appeal to the First-tier Tribunal (Tax Chamber). Grounds: a reasonable excuse for the failure (FA 2009 Sch 55 para 23), or that the penalty is wrong. Insufficient funds are not a reasonable excuse unless caused by events outside your control, and relying on someone else is not an excuse unless you took reasonable care to avoid the failure. HMRC can also reduce a penalty for special circumstances (para 16). If you appeal late you will need to give a reasonable excuse for the delay.
What is HMRC interest rate on late payments?
Interest is charged from the due date until payment (TMA 1970 s.86). The late payment rate is Bank of England base rate plus 4% from 6 April 2025 (it was base rate plus 2.5% before), which is 7.75% from 9 January 2026. Repayment interest is base rate minus 1%, with a 0.5% minimum (HMRC). Interest is simple, not compound, and runs alongside any late payment penalties. If you cannot pay: you may be able to set up a payment plan, online or by contacting HMRC; interest continues on the outstanding amount (gov.uk).
When should I file paper SA100 vs online?
The online deadline is 31 January 2028; the paper deadline is 31 October 2027. A paper return that arrives after 31 October is late even if the online deadline has not passed. Most people can file online using HMRC's free service or commercial software; online filing gives an immediate acknowledgement and calculation. You need an HMRC online services account, so set it up well before the deadline. Some returns, such as those for trustees of a registered pension scheme, have to be made on paper (gov.uk).
What records must I keep for SA + how long?
Self-employed and partnerships: 5 years after the 31 January filing deadline, so 2026/27 records until 31 January 2033. Everyone else: 1 year after the 31 January deadline, so 2026/27 records until 31 January 2029; longer if HMRC has opened an enquiry (TMA 1970 s.12B). Keep records of income and expenses, bank statements, P60s, P11Ds and P45s, interest and dividend statements, Gift Aid donations, capital gains computations and rental records. Electronic copies are acceptable. Failing to keep records can lead to a penalty of up to £3,000 (s.12B(5)). MTD users must keep records digitally.
Can I file SA late - what are my options?
File as soon as you can: the £100 penalty applies the day after the deadline, daily penalties of £10 can start at 3 months, and further tax-geared penalties at 6 and 12 months (gov.uk). Pay what you can, because late payment penalties and interest run separately. If you have a reasonable excuse, appeal the penalties. If you have several years of undeclared income, HMRC's Digital Disclosure Service lets you make a voluntary disclosure. Do not file a return you know to be inaccurate to beat the deadline: inaccuracy penalties under FA 2007 Sch 24 can be higher than late filing penalties.
How does PAYE interact with Self-Assessment?
Employees have tax deducted through their tax code, and for most that settles the year without a return. A return is still needed if one of the gov.uk conditions applies, such as untaxed income or the High Income Child Benefit Charge paid outside PAYE. The return works out the whole year: PAYE deducted is credited, and you pay any balance or get a refund. If you owe less than £3,000, file online by 30 December and pay PAYE, HMRC can collect it through your tax code. People who do not file get a tax calculation (P800) if HMRC finds they paid too much or too little through PAYE. If you have two jobs, normally only one should get your Personal Allowance.
What is the SA302 + how do I get one?
An SA302 is your tax calculation for a year, often asked for as evidence of income, for example by mortgage lenders if you are self-employed. If you file through HMRC's online services you can get it, and a tax year overview, from your HMRC online account for the last 4 years, but not until 72 hours after you sent your return. If you use commercial software, print the calculation from that software. Check that your lender accepts documents you print yourself (gov.uk).
What changes are coming to SA after April 2027 and beyond?
MTD for Income Tax: the qualifying income threshold falls from £50,000 to £30,000 (in from 6 April 2027) and then £20,000 (in from 6 April 2028), set in The Income Tax (Digital Obligations) Regulations 2026 (SI 2026/336). New late submission and late payment penalties apply from the tax year you join MTD, and from April 2027 they apply to everyone who submits a personal Self Assessment return; earlier years stay under the current rules. Late payment penalties are 3% of tax unpaid at day 15 and a further 3% at day 30 for 2026/27, rising to 4% and 4% for 2027/28, plus 10% a year from day 31. In your first year of the new penalties you have 30 days before any penalty (gov.uk). Digital platforms: since 1 January 2024, platform operators collect seller information and report it to HMRC each January; the first reports (for 2024) were due by 31 January 2025 (gov.uk).
Should I file SA myself or use an accountant?
Many people with straightforward affairs file themselves using HMRC's free online service. Consider an accountant or tax adviser if you have several income sources, rental property, overseas income, capital gains on shares, venture capital scheme claims, trusts, or residence questions. Fees vary; get a quote before engaging anyone, and check that an adviser is a member of a professional body. Whoever prepares it, you remain responsible for your return.