The 2025/26 Self Assessment tax return is due online by 31 January 2027. That can feel a long way off at the end of October, but every January we hear from sole traders, landlords and company directors across Wigan and the North West who left it late, could not find a P60, and ended up paying a bill they had not budgeted for. Filing in November or December takes the pressure off and can save you money. Here is why, and what to gather now.

The key Self Assessment dates for 2025/26

• 31 October 2026: deadline for paper returns. After this, the return must be filed online.
• 30 December 2026: file online by this date if you are employed or get a pension, owe less than £3,000, and want HMRC to collect the tax through your tax code instead of one lump sum.
• 31 January 2027: online filing deadline, and the date to pay any tax still owed for 2025/26 plus your first payment on account for 2026/27.
• 31 July 2027: second payment on account for 2026/27.

Five reasons to file early

1. You know your tax bill months in advance

Filing early does not mean paying early. The tax is still due on 31 January either way. What changes is that you know the figure in November rather than finding out in the last week of January, so you can put money aside and plan your cashflow over Christmas.

2. Payments on account will not catch you out

If your Self Assessment bill is more than £1,000, and less than 80% of your tax was already taken at source, HMRC usually asks for payments on account. These are two advance payments towards next year’s bill, each worth half of this year’s. In a good first or second year of trading, that can mean the January payment is roughly one and a half times the bill people expected. Knowing early gives you time to prepare, and if your income has dropped you can ask HMRC to reduce the payments on account.

3. Your tax could come out of your wages instead

If you are employed or receive a pension and owe less than £3,000, filing online by 30 December means HMRC can spread what you owe through your tax code over the following tax year, rather than you paying it all in one go in January.

4. Refunds arrive sooner

Plenty of people are owed money back, for example after a quiet year of trading, higher pension contributions or Gift Aid. HMRC cannot repay you until the return is in, so the sooner you file, the sooner a refund lands.

5. It tells you whether Making Tax Digital applies to you next

Making Tax Digital for Income Tax already applies to sole traders and landlords with qualifying income over £50,000. From 6 April 2027 the threshold drops to £30,000, and HMRC will use your 2025/26 return to decide whether you are in. If your combined self-employment and property income is close to £30,000, the 2025/26 figures will tell you whether you need MTD-compatible software and quarterly updates from next April. Getting the return done early gives you months to get your bookkeeping ready instead of weeks. We covered the current sign-up letters in HMRC is signing people up to MTD this month.

What happens if you miss 31 January

• A £100 penalty as soon as the return is late, even if you owe no tax.
• After three months, £10 a day for up to 90 days (up to £900).
• After six months, and again after 12 months, a further penalty of 5% of the tax due or £300, whichever is higher.
• Paying late adds interest from 1 February, plus late payment penalties of 5% of the unpaid tax at 30 days, six months and 12 months.

Those charges add up quickly, and they are almost entirely avoidable.

What to gather now

The 2025/26 tax year ran from 6 April 2025 to 5 April 2026. Depending on your situation, you will need:

• Self-employed: sales, expenses, mileage and any equipment bought in the year. If your records live in a shoebox, now is the time to sort them, or ask us about bookkeeping and monthly accounts.
• Employed or retired: your P60, any P11D for benefits like a company car, and P45s if you changed jobs.
• Landlords: rent received, letting agent statements, repairs, insurance and mortgage interest statements.
• Everyone: bank and building society interest, dividends, pension contributions, Gift Aid donations and any capital gains, such as selling shares or a second property.
• Your Unique Taxpayer Reference (UTR) and Government Gateway or GOV.UK One Login details.

If you are a company director, the 2025/26 return asks for extra details about your company, dividends and shareholding, which we explained in our post on the director Self Assessment exceptions.

Let a local accountant take it off your plate

At CMA Accountancy we prepare and file Self Assessment returns for sole traders, landlords, directors and individuals across Wigan, Standish, Ormskirk, St Helens and the wider North West. We check what you can claim, tell you exactly what you owe and when, and flag early if Making Tax Digital or payments on account will affect you. Find out more about our personal tax service in Wigan or our support for individuals and sole traders.

If you would like your return sorted well before the January rush, call us on 01257 255521 or email [email protected]. We are based in Appley Bridge, Wigan.