Self Assessment deadlines 2025/26: paper or online?
The Self Assessment deadline depends on how you file. For the 2025/26 tax year, the standard paper deadline is 31 October 2026, while the standard online deadline is 31 January 2027. Choosing a filing route now gives you time to organise the figures and understand the payment that follows.
This guide is for sole traders, landlords and individuals preparing a personal tax return in Bromley, London and across the UK. It explains the practical decisions to make this autumn, including what to do if you are new to Self Assessment or already using Making Tax Digital.
The dates to put in your diary
The return covers the tax year from 6 April 2025 to 5 April 2026. Under HMRC’s standard Self Assessment deadlines:
Paper return: HMRC must receive it by 11:59pm on Saturday 31 October 2026.
Online return: submit it by 11:59pm on Sunday 31 January 2027.
Tax payment: the normal deadline for the remaining 2025/26 balance is 31 January 2027.
Tax-code collection: eligible taxpayers filing online need to submit by 30 December 2026.
Check any specific deadline in your HMRC notice. Late registration and some specialist returns have different arrangements. A personal Self Assessment deadline also should not be used as the filing date for a limited company’s accounts or Corporation Tax return.
Paper filing: delivery matters
Posting a tax return on 31 October does not satisfy a requirement for HMRC to receive it by that date. With the deadline falling on a Saturday in 2026, leave a realistic delivery margin instead of planning around the last collection.
If you are filing on paper, use the correct year’s SA100 and any supplementary pages required for your circumstances. HMRC’s guidance on sending a return links to the forms and explains how to obtain them.
Before sending it, work through this short check:
Confirm your name, Unique Taxpayer Reference and the year shown on the return.
Check that every relevant income source is covered by the main form or the appropriate supplementary pages.
Read the declaration, complete the required signature and date, and follow the return’s instructions.
Keep a complete copy and evidence of posting or delivery. Evidence of posting alone does not establish that HMRC received it on time.
If the paper route is becoming impractical, check your online options before submitting anything. Avoid sending a duplicate return simply because you are unsure whether the first one arrived; establish what has been submitted and seek help with the correct next step.
Online filing: check access and suitability early
For many individuals, online filing offers a useful extra preparation window. However, the extra time only helps if you can access the service and use a filing method that supports your circumstances.
Start at HMRC’s official online filing page. You need your UTR and sign-in access. First-time filers must register, while someone who previously registered may need to reactivate their account. Test this now, rather than discovering a problem in January.
You can save an unfinished online return and come back to it. Treat that as preparation: a saved draft is not a submitted return. After filing, retain the confirmation and a copy of the completed return and calculation.
HMRC’s free online service does not support every situation. Examples include partnership returns, trust and estate returns, and people who lived abroad as non-residents. Commercial software or the relevant paper forms may be needed. Check the service’s exclusions before committing to a route; being unable to use the free service does not necessarily mean that all online filing is unavailable.
If you appoint an accountant, agree who is providing the records, reviewing the draft and submitting the return. Put those dates in your diary. An engagement that starts late in January may leave little time to resolve missing information.
Gather records for the whole return
A useful preparation folder brings together both business and personal information. Your bookkeeping report may explain trading profit, but it will not necessarily include employment income, savings, dividends or rental activity.
Start with the previous return as a checklist of income sources, then ask what changed during 2025/26. New work, a property sale, a change of job or an overseas income source may require information that was absent last year.
Business records: sales, expenses, invoices, receipts and bank statements, with unexplained transactions identified.
Employment and pensions: relevant P60s, P45s, benefit information and pension statements.
Property: rental statements and supporting records for costs, with property transactions flagged for separate review.
Other personal information: interest and dividend statements, pension contributions, Gift Aid records and details of relevant disposals.
Tax already paid: your Self Assessment statement, payments on account and any relevant tax-deduction certificates.
This is a preparation list, not a statement that every item is taxable or deductible in the same way. The treatment depends on the facts. Where a figure is uncertain, record the question beside it rather than silently guessing.
HMRC’s business record guidance requires accurate records that identify business transactions. Compare your bookkeeping totals with the underlying evidence and look for missing or duplicated entries. Keep the supporting records even though they are not normally sent with the return.
Also confirm the accounting method used. Under HMRC’s accounting-method guidance, cash basis records money when received or paid, while traditional accounting follows different timing rules. A list of invoices and a list of bank receipts can therefore produce different figures. Do not switch between them simply to make a total agree.
Filing early does not normally bring payment forward
Finishing your return in October or November can turn an unknown bill into a number you can plan around. The normal January payment date still applies. Keep the filing task and the payment task as two separate entries in your diary.
Your January amount may include both the remaining bill for 2025/26 and a first payment on account towards 2026/27. HMRC’s payments on account guidance explains when these advances apply and where to check them. Do not assume the figure labelled “tax for the year” is the whole amount you need in January.
For a simple budgeting illustration, suppose your confirmed January amount is £3,600 and you have already reserved £1,200. The remaining funding gap is £2,400. Setting aside £800 in each of November, December and January would cover it, provided the final transfer reaches HMRC on time. These are illustrative savings figures, not a calculation of anyone’s tax liability.
If current-year income has fallen, our guide to reducing payments on account explains the evidence to consider. Reducing an advance payment needs a supportable estimate; it does not remove tax already owed for the completed year.
Allow for payment processing too. HMRC’s payment guidance gives different lead times for different methods. For weekend deadlines, it generally requires payment on the preceding working day, with exceptions for Faster Payments and online card payments. Since 31 January 2027 is a Sunday, choose your method and transfer date deliberately.
Could HMRC collect the bill through your tax code?
Some people who already pay tax through PAYE can have an eligible Self Assessment bill collected through their salary or pension. This can be relevant to an employee with additional income, but it is subject to conditions.
Under HMRC’s tax-code payment rules, the bill must be less than £3,000, you must already pay through PAYE, and you must file on paper by 31 October or online by 30 December. There must also be sufficient PAYE income and the collection must meet HMRC’s limits.
You cannot make a part payment just to bring a bill of £3,000 or more below the threshold. Check eligibility and what your account says before removing a January payment from your budget. Filing by the earlier date alone is not a guarantee that the bill can be collected this way.
Late registration, missing figures and Making Tax Digital
If you should have registered by 5 October but have not done so, act now. HMRC’s deadlines guidance explains that people registering after 5 October 2026 receive a filing deadline three months from its letter or email. The tax still needs to be paid by 31 January 2027. A later filing date is therefore not automatically extra time to fund the bill.
If you do not know your profit for the whole year, HMRC’s return guidance allows provisional figures, which must be identified and corrected when the final figures are available. Get help deciding whether that applies to your situation. Keep the reasoning and evidence behind any provisional amount.
Making Tax Digital does not remove the 2025/26 return. HMRC’s October 2026 Self Assessment reminder confirms that people signed up for MTD for Income Tax still need to file that return in their usual way. Keep the completed year’s return separate from your current digital records and quarterly-update tasks. Our Making Tax Digital support can help organise those ongoing obligations.
Your practical next steps this week
Choose the route: confirm paper, HMRC online or suitable commercial software.
Verify the deadline: check the tax year and any specific HMRC notice.
List missing records: give each item a person responsible and a target date.
Plan review and submission: leave time for questions and retain the filing receipt.
Plan payment separately: check the full January amount, available savings and processing time.
Mysimplytax provides Self Assessment services for individuals and sole trader accountancy support, with offices in Bromley and London and support across the UK. Share your filing position and the records you have available so the remaining work can be identified promptly.
Guidance checked against HMRC sources on 26 October 2026. This article covers general UK filing arrangements; individual circumstances and specific HMRC notices may change the steps required.
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