The 31 January 2026 deadline is approaching faster than you might think.Â
For the 2024/25 tax year, more than 11.5 million people will need to file their self-assessment tax return, and if recent years are any indication, roughly 1.1 million will miss the deadline and face automatic penalties.
The good news? With proper planning and the right information, you can file confidently and avoid the stress of the final days of January, when HMRC’s systems are under strain and panic sets in.
Understanding the 2026 Self-Assessment Timeline
Let’s start with the dates you need to mark in your calendar. The self-assessment system works backwards, so the 2024/25 tax year (which ran from 6 April 2024 to 5 April 2025) needs to be reported by specific deadlines in 2025 and 2026:
- 5 October 2025 was the deadline to register if you were newly self-employed or had untaxed income for the first time. If you missed this, you should contact HMRC immediately.
- 31 October 2025 was the paper filing deadline. Most people file online now (97.36% of returns in the last tax year), but if you prefer paper, that date has already passed.
- 30 December 2025 is an important one if you owe less than £3,000 and want HMRC to collect the tax through your PAYE code, spreading the cost across the next tax year.
- 31 January 2026 is the main event. This is when your online return must be filed and any tax owed must be paid. Miss this date, and you’ll face an immediate £100 penalty, even if you don’t actually owe any tax.
- 31 July 2026 is when your second payment on account is due if you’re required to make these advance payments.
What the Numbers Tell Us
Here’s something interesting: last year, 732,498 people filed their returns on the deadline itself. That’s more than half a million people leaving it until the very last moment.Â
The peak filing hour? Between 16:00 and 16:59, when 58,517 people submitted their returns. Another 31,442 left it until between 23:00 and 23:59 on the final day.
Filing early makes sense for several reasons. More than 3.5 million people had already submitted their 2024/25 returns by October 2025, giving them nine months of breathing room. These early filers know their tax bill well in advance, can plan their finances accordingly, and avoid the technical glitches that often plague HMRC’s systems during the January rush.
The Cost of Missing the Deadline
The penalties for late filing aren’t trivial, and they escalate quickly:
- Day 1 after the deadline: An automatic £100 fine, regardless of whether you owe tax or have already paid it.
- After 3 months: Daily penalties of £10 kick in, adding up to a maximum of £900 over 90 days.
- After 6 months: A further penalty of either 5% of the tax due or £300, whichever is greater.
- After 12 months: Another 5% or £300 charge on top of everything else.
Late payment penalties are separate from late filing penalties. Interest starts accruing immediately after 31 January 2026, and you’ll face a 5% penalty if you still haven’t paid after 30 days, with additional penalties at six months and twelve months.
The total cost of being late can mount up quickly. Someone who files six months late and owes £5,000 in tax could face penalties exceeding £1,500 on top of their original tax bill.
Who Needs to File in 2026?
Self-assessment catches more people than you might expect. The obvious cases include sole traders and those in business partnerships, but you also need to file if:
- You earned over £100,000 from any source, even if your employer handled all your tax through PAYE. High earners need to file because you may need to repay some of your personal allowance.
- You received rental income exceeding £2,500 before expenses, including income from property abroad or holiday lets.
- You’re a company director taking dividends or benefits from your company.
- Your savings, investments, or dividends generated £10,000 or more in income.
- You sold assets like shares or a second property and need to report Capital Gains Tax.
- You receive Child Benefit and either you or your partner earn over £60,000, triggering the High Income Child Benefit Charge.
So make sure you look at your situation if you fall into these buckets. Unsure? We can help.Â
Looking Ahead: Making Tax Digital
A major change is on the horizon that will affect many self-assessment filers.Â
From 6 April 2026, Making Tax Digital for Income Tax Self Assessment (MTD for ITSA) launches for sole traders and landlords with qualifying income over £50,000.
This means quarterly digital reporting instead of one annual return. The threshold drops to £30,000 from April 2027 and £20,000 from April 2028. HMRC will use your 2024/25 tax return to determine whether you need to comply with Making Tax Digital from April 2026, so filing accurately and on time this year matters more than ever.
The first wave of taxpayers entering Making Tax Digital will benefit from a penalty easement for their first four quarterly updates in 2026/27, but penalties will still apply for late final declarations and late payment.
Look at our MTD for ITSA guides for more information.Â
Need to File This January? Here’s What to Do Now
With the deadline upon us, time is tight but not impossible. Whether you’re filing for the first time or you’ve been putting it off, working through these steps systematically will get you over the line.Â
| Task | What You Need to Do | Done? |
| Check your UTR and login | Locate your Unique Taxpayer Reference (10-digit number) and make sure you can access your Government Gateway account. If you’ve forgotten your password, reset it now. | â–¡ |
| Gather income records | Collect all evidence of income: P60/P45 forms from employment, business sales records, bank statements showing interest, dividend vouchers, and rental income records. | â–¡ |
| Compile expense receipts | If self-employed, gather all receipts for allowable business expenses. Landlords need records of property maintenance, insurance, and management fees. | â–¡ |
| Note any benefits received | Include P11D forms showing company benefits like cars or health insurance. Don’t forget pension contributions you want tax relief on. | â–¡ |
| Check for taxable payments | Did you receive any government support payments, maternity allowance, or income from trusts? These may need declaring. | â–¡ |
| Log into HMRC online | Access your Self Assessment account and start your return. The system saves your progress, so you can complete it in stages. | â–¡ |
| Fill in all sections | Work through each section carefully. The online system guides you and calculates as you go. Take your time with figures. | â–¡ |
| Review before submitting | Check all numbers twice. Look for common errors like transposed digits or missed income sources. | â–¡ |
| Submit your return | Once satisfied, submit online. You’ll get instant confirmation and see your tax calculation immediately. | â–¡ |
| Pay your tax bill | Use online banking, debit card, or the HMRC app. Remember: your payment must clear by midnight 31 January 2026. | â–¡ |
Remember that HMRC’s systems experience high traffic in late January. Don’t rely on filing in the final hours of 31 January. If you encounter technical issues during peak times, you won’t have time to resolve them before the deadline.
How Double Point Can Help
Self-assessment doesn’t need to be overwhelming. At Double Point, our chartered accountants handle everything from registration through to filing, ensuring you meet deadlines and claim every allowable expense and relief.
We’re particularly experienced in helping clients prepare for the transition to Making Tax Digital, select appropriate software, and set up systems that will serve them well beyond 2026.
With the 31 January deadline almost here and Making Tax Digital launching in April, now is the time to get your tax affairs properly organised.Â
Book a consultation with Double Point today, and let our team show you how straightforward self-assessment can be when you have expert support.