Self Assessment deadlines and penalties UK: 2025/26 filing guide
For the tax year from 6 April 2025 to 5 April 2026, the main Self Assessment dates are 5 October 2026 to tell HMRC you need a return, 31 October 2026 for most paper returns, and 31 January 2027 for online filing and payment. Missing a date can create separate registration, filing, payment and interest consequences. This guide explains each stage, what the penalties can become and the practical steps to take if you are already late.
Important information
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Who this guide applies to
- sole traders and freelancers
- landlords
- people with untaxed income
- company directors and shareholders
- new Self Assessment taxpayers
- people who have missed a deadline
Common costs to consider
- allowable business expenses
- property expenses
- professional fees
- platform and payment charges
- business travel and mileage
- software and record-keeping costs
The Self Assessment timeline for 2025/26
The 2025/26 tax year began on 6 April 2025 and ended on 5 April 2026. Once the year ended, a taxpayer could prepare the return using final income, expense and tax records. A person who needs to complete a return for the first time, or is returning after a year in which no return was required, should normally tell HMRC by 5 October 2026. HMRC must receive most paper returns by 31 October 2026. The online return and any balancing tax are normally due by 11:59pm on 31 January 2027. A taxpayer who wants an eligible small bill collected through a PAYE tax code generally needs to submit online by 30 December 2026, subject to HMRC’s conditions. Payments on account can create another deadline on 31 July. These dates are linked but perform different jobs: notification, filing and payment. Completing one does not automatically complete the others. Put every relevant date in a calendar and confirm the exact obligations shown in the HMRC account.
5 October 2026: tell HMRC you need to file
The 5 October deadline is commonly described as the deadline to register for Self Assessment. It applies where a person needs a return for the previous tax year and has not sent one before, or had registered previously but did not need to send a return for the 2024/25 tax year. Sole traders, new landlords and people with other untaxed income should use HMRC’s checker because the filing obligation depends on the full circumstances. The £1,000 trading and property allowances can remove the need to report some small gross income, but exceptions apply. Registering after 5 October does not make filing impossible. Tell HMRC as soon as possible and preserve the confirmation. HMRC says a failure-to-notify penalty may arise where registration is late and the tax due is not fully paid by 31 January. The amount is linked to unpaid tax and behaviour rather than being the same automatic amount in every case. Early registration also leaves time to receive or recover a UTR and online access.
31 October 2026: the usual paper-return deadline
A taxpayer choosing a paper Self Assessment return for 2025/26 should normally make sure HMRC receives it by 11:59pm on 31 October 2026. Posting it on the deadline is not the same as HMRC receiving it. Use the correct forms and supplementary pages, keep a full copy and allow delivery time. If the paper deadline is missed, filing online by 31 January may still avoid a late filing penalty, provided the return is eligible for online filing and online access is ready. Do not submit both a paper and online return for the same year simply because the paper delivery is uncertain; contact HMRC if status needs checking. Some specialist taxpayers have different return routes or deadlines, including trustees of registered pension schemes, non-resident companies and certain partnerships with a company partner. This guide focuses on the ordinary individual timetable. A person whose circumstances require specialist forms should follow the instructions attached to those forms rather than assuming the standard deadline applies.
30 December 2026: paying through a PAYE code
HMRC may be able to collect an eligible Self Assessment amount through a PAYE tax code where the taxpayer files online by 30 December and meets the conditions. This does not mean every bill can be coded out, and it is not an extension of the ordinary return deadline. The amount, PAYE income and timing all matter, and HMRC decides whether coding is possible. If collection through the code is desired, file well before the date so errors, missing income or access problems can be resolved. Check the calculation and later tax code because collection is spread through payroll rather than paid as one transfer. A taxpayer who misses the 30 December date can still file online by 31 January but should plan another payment method. Do not delay filing solely to wait for a final January payment if all records are ready; early filing provides more time to understand whether coding, a budget plan or direct payment is realistic.
31 January 2027: online filing and payment
HMRC must normally receive the online 2025/26 return and balancing payment by 11:59pm on 31 January 2027. These are separate obligations that happen to share a deadline. Submitting the return without arranging payment can lead to late-payment penalties and interest. Making a payment without submitting the return can still lead to late-filing penalties. Online filing can be completed earlier; doing so does not normally bring the 31 January payment date forward. File early enough to review the calculation, confirm PAYE already deducted, check student loan information and understand payments on account. Payment methods take different lengths of time, so use HMRC’s current payment guidance rather than assuming a transfer is instant. Include the correct payment reference. If the calculated amount appears wrong, check the entered income, expenses, tax deducted and payments on account before overriding anything. A calculator can estimate the cash needed, but the submitted return and HMRC statement remain the operational record.
31 January and 31 July: payments on account
Payments on account are advance payments towards the following year’s Self Assessment bill. They are usually split into two instalments, one due on 31 January and one on 31 July, and are generally based on the previous year’s relevant tax. This can make the first large January bill feel like 150% of one year’s liability: the balancing payment for the year just filed plus the first half-payment towards the next year. The second half follows in July. They are not an extra tax rate. If the advance payments do not cover the next final bill, a balancing amount will be due later; if they are too high, the account can be adjusted or repaid. A taxpayer who genuinely expects a lower bill may claim to reduce payments on account, but reducing them too far can lead to interest on the shortfall. Base a reduction on current income and expense evidence. The payment calculator on this site models the timing but cannot determine HMRC eligibility in every case.
Late filing penalties
Under the standard Self Assessment penalty rules described by HMRC, an online return filed after the deadline can receive an initial £100 penalty even if no tax is due or the bill was paid on time. After three months, additional daily penalties of £10 can apply for up to 90 days, creating a maximum £900 daily-penalty amount. At six months, a further penalty can be 5% of the tax due or £300, whichever is greater. At twelve months, another 5% or £300 can apply, with more severe treatment possible in serious cases. Partnership returns can generate penalties for each partner. These filing penalties are separate from late-payment penalties and interest. The fastest way to stop additional filing penalties accumulating is usually to submit the missing return, even if a payment problem remains. If exact figures are not available, HMRC provides guidance for returns where profit is provisional. Do not leave a return unfiled merely because the tax cannot yet be paid; deal with filing and payment as two workstreams.
Late payment penalties and interest
HMRC’s standard Self Assessment guidance states that late-payment penalties can be 5% of the unpaid tax at 30 days, six months and twelve months after the due date. Interest is also charged on overdue tax. The penalty is based on the amount still unpaid at the relevant point, so paying as much as possible can reduce exposure even where the full balance is unavailable. Check the HMRC statement because the account may include a balancing payment, payment on account, earlier debt, interest or penalties. Use an approved payment method and correct reference. If you cannot pay in full, contact HMRC promptly or review whether an online Time to Pay arrangement is available; ignoring the balance is rarely the least costly option. A Budget Payment Plan is different: it lets an up-to-date taxpayer make regular advance payments towards a future bill. Neither arrangement changes the requirement to file. Keep confirmation of payments and any agreed plan, then reconcile the HMRC account after processing.
Making Tax Digital penalty changes
Making Tax Digital for Income Tax changes filing frequency and introduces a points-based penalty system for people from the tax year they join the MTD regime. HMRC states that sole traders and landlords with qualifying income above the applicable entry threshold come into scope in phases. The current HMRC guidance for 2026/27 says there are no penalties for missing a quarterly-update deadline during that first year, although digital records and quarterly updates are still required before the tax return can be completed. The new late-submission and late-payment rules apply according to the person’s MTD start year, while current penalties continue for earlier returns such as the 2025/26 return due on 31 January 2027. This transition means a generic penalty article can become misleading if it does not identify the tax year and MTD status. Check the dedicated HMRC MTD penalty page before relying on the standard amounts above for a 2026/27 or later obligation.
Reasonable excuse and appealing a penalty
A taxpayer can appeal a Self Assessment penalty where there was a reasonable excuse. HMRC looks at the individual facts, what prevented compliance and whether the taxpayer acted without unreasonable delay after the excuse ended. Serious illness, bereavement, service failure or an unexpected event may be relevant depending on evidence and timing; simply finding the tax system difficult or relying on someone without checking is not automatically enough. Read the penalty notice, identify the tax year, deadline and appeal date, and provide a clear chronology with supporting documents. Pay the underlying tax where possible because an appeal against a penalty does not necessarily stop interest on unpaid tax. If the return is outstanding, submit it while the appeal is considered. Keep copies of the appeal and HMRC response. Where the amount is significant, several years are involved or HMRC alleges deliberate behaviour, obtain professional advice rather than relying on a short template from the internet.
What to do today if you have missed a deadline
First, establish exactly what is missing: registration, a return, a payment, a payment on account or a response to HMRC. Sign in through GOV.UK and compare the account with your records. Register or reactivate Self Assessment if necessary. Gather income, expenses, PAYE documents and tax already paid, then file the return as soon as practical. Do not wait for perfect bookkeeping while penalties continue; use HMRC’s process for provisional figures where genuinely necessary and amend later. Pay what you can using the correct reference and contact HMRC about the remainder. Review the notice for an appeal where a reasonable excuse exists. Correct the system that caused the failure: calendar reminders, monthly reconciliation, secure access to the UTR, an earlier accountant handover and a tax reserve. Scam messages often intensify around deadlines, so navigate directly to GOV.UK rather than using an unexpected payment link. Document every action and confirmation number.
File early and separate calculation from cash flow
Early filing improves options. It gives time to correct missing PAYE details, understand a larger-than-expected bill, check whether PAYE coding is available, arrange a payment plan and prepare for payments on account. It also reduces the risk that an expired password, delayed UTR or software problem appears in the final hours. Filing early does not mean paying immediately under the normal timetable. Build a year-round process instead: update records monthly, estimate profit quarterly, move a percentage of cash into a tax account and run the payment-on-account scenario before the tax year ends. Keep personal cash-flow planning separate from the legal filing date. A low bank balance does not remove the return obligation, while a healthy bank balance does not prove the calculation is correct. Use calculators to understand possible amounts, then verify the final return against HMRC guidance, actual records and professional advice for complex positions.
Official references
Frequently asked questions
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