Most people treat 31 January as the deadline to file their tax return. But really, it’s the last date to file and pay, not the first opportunity to do either.
You can file online from 6 April, as soon as the tax year ends. Even so, HMRC’s figures showed that at the start of January 2026, around 5.65 million people still hadn’t filed their return for the 2024/25 tax year.
Leaving it until January is perfectly legal, but it has costs that aren’t obvious. Filing in the autumn affects how you can pay, how much notice you get of your bill, when you receive any refund and how long HMRC has to open an enquiry.
Each of these directly affects your money, and all depend on your filing date.
Read on so we can convince you of the benefits of filing your tax return early.
When You Can File, and When You Have to Pay
The tax year ends on 5 April, and HMRC accepts online returns for that year from 6 April. Paper returns must reach HMRC by 31 October, and online returns by 31 January. Any tax you owe is due on 31 January, whichever date you file, so filing in October doesn’t mean paying in October.
More people are choosing to file early. HMRC reported that almost 740,000 returns for the 2025/26 tax year were filed in April 2026, a record for the month, with more than 298,900 in the first week alone.
That’s still a small share of the more than 12 million returns HMRC expects to receive this year.
Paying Your Tax Through Your Tax Code
If you’re employed or receive a company pension, filing early can help you avoid a lump-sum payment altogether.
HMRC will collect the tax through your PAYE tax code for the following year, spreading it across your pay, as long as you meet three conditions:
- You owe less than £3,000: The limit applies to the amount you owe when HMRC processes your return. Paying off part of a larger bill to get below it doesn’t count.
- You already pay tax through PAYE: You need a salary or company pension with a tax code HMRC can adjust.
- You file in time: Online returns must be filed by 30 December, and paper returns by 31 October.
HMRC won’t use this route if you don’t have enough PAYE income, if you’d end up paying more than half your PAYE income in tax, or if you’d pay more than twice as much tax as you normally do. It applies automatically unless you opt out on your return. Your employer receives the new tax code, but not the reasons behind it.
The result is an interest-free instalment plan. Laura is a higher-rate taxpayer who lets out a flat and owes £1,800 on her rental profit. If she files online by 30 December, HMRC reduces the tax-free allowance in her tax code by £4,500 for the next tax year.
At 40%, that amounts to £1,800, collected as 12 monthly deductions of £150. Because most of her tax is already collected through her salary, she doesn’t have payments on account either, so there’s nothing to pay on 31 January.
Knowing Your Payments on Account Before January
Payments on account are advance payments towards next year’s tax bill. HMRC asks for them if your last Self Assessment bill was £1,000 or more, unless more than 80% of your tax was already collected at source.
Each payment is half of the previous year’s Income Tax and Class 4 National Insurance, with one due on 31 January and the other on 31 July. Capital Gains Tax and student loan repayments aren’t included in the calculation.
They cause the most difficulty in someone’s first year of Self Assessment, because the first January bill includes the full tax for the year just ended plus the first payment on account for the current year.
Tom started freelancing, and his first year’s tax bill is £6,000. On 31 January he owes £9,000, followed by another £3,000 on 31 July. Filing in October gives Tom three months to plan for that figure, instead of discovering it a few days before it’s due.
Filing early also helps if your income has fallen. Once you know what HMRC will ask for, you can reduce your payments online or on form SA303, as long as you claim by 31 January after the end of the tax year. If you reduce them too far, HMRC charges interest on the shortfall from each original due date.
To spread the cost of future bills instead, you can set up a budget payment plan with weekly or monthly Direct Debits, provided you’re up to date with your previous payments.
Getting a Refund Months Sooner
HMRC can repay overpaid tax only after you’ve filed a return showing it. That matters for anyone whose payments on account exceeded their final bill, and for people who had too much tax deducted before they were paid.
Construction Industry Scheme subcontractors are a common example, since they usually have 20% deducted from their payments before any expenses are taken into account.
A return filed in October starts the repayment process more than three months earlier than one filed on 31 January. For a subcontractor owed £2,500, that can mean having the money before Christmas rather than in February or March.
How Filing Early Affects HMRC Enquiries
Some people delay filing because they believe an early return attracts more HMRC attention.
There’s no published rule linking filing date to selection, and the enquiry window favours filing early. When you file on time, HMRC has 12 months from the date it receives your return to open an enquiry, according to its Self Assessment manual.
File on 15 October and that window closes on 15 October the following year. File on 31 January, and it stays open until the following 31 January.
Filing early doesn’t stop you from correcting mistakes. You can amend your return up to 12 months after the 31 January deadline, so you can still update an October return if you find a missing figure later.
HMRC can also raise a discovery assessment outside the enquiry window in some circumstances, such as where tax was underpaid because of carelessness, so accuracy matters more than timing. Our guide to HMRC’s error checks explains how returns may be selected for review.
What You Need Ready to File in the Autumn
By October, most of the paperwork for the previous tax year has already arrived. Gathering it in one go makes the return quicker to complete and easier to check. For most people, that means:
- Employment details: Your P60 for the year, and any P11D showing taxable benefits such as a company car.
- Business records: Income and expenses for your accounting period, including mileage and use-of-home claims.
- Property figures: Rent received, letting costs and statements showing the mortgage interest you paid.
- Savings and investments: Interest and dividend statements, and details of any shares or property you sold during the year.
- Reliefs: Pension contributions and Gift Aid donations made during the year.
Filing Your Return With Double Point This Autumn
Filing a return in October or November gives you time to plan your January payment, apply to reduce payments on account, and receive any refund sooner. For employees and pensioners with a small bill, it can mean no January payment at all.
At Double Point, we prepare and file Self Assessment returns throughout the autumn. We’ll tell you exactly what you owe and when it’s due, check whether your tax can be collected through your tax code, and review whether your payments on account should be reduced.
Book a free consultation and we’ll check which of these options apply to you.
Disclaimer: General information only, not advice. Rules and figures can change. Take advice on your own circumstances before acting.