Self Assessment deadline 31 January 2027: what to file, pay and prepare

The next major Self Assessment date is 31 January 2027. For many sole traders, landlords, company directors and people with untaxed income, it is the date by which both the online tax return and any tax owed must reach HMRC.

This guide explains what the deadline covers, who usually needs to file, what to gather now and what tends to hold returns up. Dates and amounts below were checked against GOV.UK on 5 November 2026.

What the 31 January 2027 deadline covers

The deadline relates to the 2025 to 2026 tax year, which ran from 6 April 2025 to 5 April 2026. According to GOV.UK's Self Assessment deadlines page:

online tax returns must be submitted by 11:59pm on 31 January 2027
any Self Assessment tax you owe must be paid by 11:59pm on 31 January 2027
paper returns had an earlier deadline of 11:59pm on 31 October 2026

If you registered for Self Assessment after 5 October 2026, HMRC will send you a letter or email with a different filing deadline (3 months from the date of that letter or email), so check what HMRC has told you. Any tax owed is still due by 31 January 2027.

Payments on account

31 January is often more than a single payment. If you make payments on account, the first payment towards your 2026 to 2027 bill is also due on 31 January, with a second payment due by 31 July.

GOV.UK explains that each payment on account is usually half of the tax you owed for the previous year. You do not have to make them if your last Self Assessment bill was less than £1,000, or if you paid more than 80% of the tax you owed outside Self Assessment, for example through your tax code.

If your income turns out higher than the estimate, you may also have a balancing payment to make. This is worth planning for, as the 31 January total can be larger than people expect.

30 December 2026 if you want to pay through your tax code

Some people can have Self Assessment tax collected through their PAYE tax code instead of paying in one go. GOV.UK sets out the conditions for paying through your tax code:

you owe less than £3,000 on your tax bill
you already pay tax through PAYE, for example as an employee or through a company pension
you submit your online return by 30 December

For the 2025 to 2026 return, the online deadline for this option is 11:59pm on 30 December 2026.

Who needs to file a Self Assessment return

The rules depend on your income and circumstances. GOV.UK lists situations where you must send a return, including if in the last tax year you:

were self-employed as a sole trader and earned more than £1,000 before deducting costs
were a partner in a business partnership
had to pay Capital Gains Tax on something you sold or disposed of
had to pay the High Income Child Benefit Charge and do not pay it through PAYE

You may also need to file if you had untaxed income such as rental income, tips and commission, savings interest, dividends or foreign income.

If you are unsure, use HMRC's check if you need to send a Self Assessment tax return tool. If HMRC has written to ask you to file, you need to send a return by the deadline in that letter.

Records to gather now

Starting early gives you time to find missing paperwork and ask questions. Depending on your income sources, useful records include:

your Unique Taxpayer Reference (UTR), and a check that you can sign in to your HMRC online account (never share those sign-in details)
P60s, P45s or P11Ds for any employment
sales invoices, receipts and bank statements for self-employment
records of business expenses you intend to claim
rental income and allowable property costs, including any jointly owned property
dividend vouchers and statements of savings interest
details of pension contributions and Gift Aid donations
records of any assets sold and their purchase costs
details of foreign income and any foreign tax paid

Sole traders and partners must keep records of business income and expenses for their return, as explained in GOV.UK's guidance on business records if you're self-employed. These records must be kept for at least 5 years after the 31 January submission deadline of the relevant tax year.

Common reasons returns get delayed

Most late returns are not caused by complicated tax. They are caused by small practical problems that surface in January. Common examples include:

Access issues. Lost Government Gateway details or a missing UTR can take time to sort out, so check you can sign in well before the deadline.
Registering late. You needed to tell HMRC by 5 October 2026 if you had to file for the first time for 2025 to 2026. GOV.UK notes that telling HMRC after that date could result in a penalty.
Incomplete bookkeeping. Unreconciled bank accounts or missing receipts slow everything down.
Forgotten income. Small amounts of interest, dividends, property income or overseas income are easy to overlook.
Waiting for third-party documents. Statements from employers, pension providers or investment platforms may need chasing.
Not budgeting for payment. Filing on time does not remove the need to pay on time.

Penalties for missing the deadline

HMRC sets out Self Assessment penalties on GOV.UK. For a late return:

an initial £100 penalty
after 3 months, additional daily penalties of £10 per day apply, up to a maximum of £900
after 6 months, a further penalty of 5% of the tax due or £300, whichever is greater
after 12 months, another 5% or £300, whichever is greater

For late payment, penalties of 5% of the tax unpaid apply at 30 days, 6 months and 12 months, and interest is charged on the amount owed. If you have a reasonable excuse, you can appeal against a penalty.

When to get help

Support can be useful if you have several income sources, rental property, foreign income, a first year of self-employment, or records that need tidying before a return can be prepared. It also helps to get started early if you are not sure whether a particular item should be included.

An accountant can help you organise income and expense schedules, prepare the return and explain the calculation before you approve it. You remain responsible for checking the return and making sure it is accurate and complete. Agree early which records are needed, who reviews the figures and how any submission will be handled, so there is time to resolve questions before January.

Sources

TaxSpex can prepare the agreed income and expense schedules and Self Assessment return for your review, with submission support only where agreed and authorised. See Self Assessment support or Accounting for sole traders. This article is general information, not advice for your circumstances.