Martin Lewis has spoken out about a key deadline in 2026 and explained exactly who has to take action. The personal finance expert explained a key £10,000 savings threshold would mean filling out the forms.
And he said anyone who is sent a self-assessment tax form ‘has to do it even if you think you don’t have to’. He explained that the deadline is January 31 and added that even if you don’t know what you owe suggested making a “rough guess” of what you owe and paying that amount before. This stops the 7.75% interest from building up, even if you have to amend the actual form slightly later.
Mr Lewis said in a new video on X: “Do you need to do a tax return? If you do, it’s urgent. The self-assessment tax deadline is the end of this month, the 31st of January, and 5.6 million people who do need to file one haven’t done it yet. If that’s you, get your skates on because if you miss a deadline, there’s a 100 quid fine, but more painfully, there’s also 7.75% interest on unpaid tax.
“In fact, what that means is even if you can’t do the form in time, have a rough guess of what you owe and pay that because that would reduce any interest you needed to pay for late payment of your tax.”
So who needs to do this?
Mr Lewis explained: “Well, the first thing to say is anyone HMRC has told to do so. If you’ve been sent a self-assessment tax form to do it, you have to do it, even if you don’t think you have to, you have to do it. Now, that’s more likely with people who are higher 40% or additional top 45% rate taxpayers or people with complex tax affairs.
“The other main categories of who should do it if you haven’t been sent a self-assessment form are those who are self-employed and who’ve earned over £1,000 in the tax year. So remember, this is the tax year from the 6th of April 2024 until the 5th of April 2025.
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“Anyone who gets child benefit and earned over £60,000 in the tax year and hasn’t opted to change your tax code so that you pay it through that way. Anyone who’s earned over £10,000 from savings interest or investment dividends in the tax year.”
Leaving it late might mean people struggle to get through on the HMRC phone lines, he added: “Now, there are some smaller categories—those are the main ones. If that’s you and you need to do this return, then don’t delay because the later you leave it, the more clogged up HMRC’s phone lines get if you need to speak to them, plus accountants, they’re also busy, and getting it all filed if you need help, it all gets a lot trickier and it will be a lot more painful. Doing it early will relieve some of that pain, though you’ll still have to pay.”
With less than a month to the January 31 deadline, 54,053 people saw in the new year by filing their tax return for 2024-25 over New Year’s Eve and New Year’s Day.
Some 3,927 people filed their return between 11.00am and 11.59am on December 31 – the most popular time over the two days. More than 6.36 million taxpayers have submitted their tax return and nearly 5.65 million still need to complete their self-assessment form before the deadline.
Those who miss the deadline could face an initial late filing penalty of £100, followed by possible further penalties. The £100 fixed penalty applies even if there is no tax to pay or if the tax due is paid on time.
Myrtle Lloyd, HMRC’s chief customer officer, said: “What better way than to ensure your tax affairs are in order for another year than completing your tax return.
“If you have yet to start, the clock is ticking, go to gov.uk and start today.”
HMRC said people can start their tax return, save it and revisit it as many times as they need to before they submit it. Once they have sent it, the bill does not have to be paid straight away, but does need to be paid before the January 31 deadline, the revenue body said.
People can set up notifications in the HMRC app to ensure they know when payments are due so they do not miss a deadline.
People who are unable to meet the deadline are being urged to tell HMRC before January 31. HMRC said it will treat those with reasonable excuses fairly.
1. Where to File
The official government portal is the only place you should submit your return online:
2. Essential Identification
Before you start the form, make sure you have these two numbers:
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UTR (Unique Taxpayer Reference): A 10-digit number sent to you by HMRC when you registered.
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National Insurance Number: Found on your payslip, P60, or in your personal tax account.
3. Document Checklist
Depending on your circumstances, you will need the following records for the tax year (6 April 2024 to 5 April 2025):
If you were employed during the year:
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P60: Shows the income you’ve already paid tax on.
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P45: If you left a job during the tax year.
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P11D: If you received benefits like a company car or private health insurance.
If you are self-employed or a landlord:
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Income Records: All invoices, rental receipts, or a summary of your total turnover.
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Expense Records: Receipts and bank statements for business costs (office rent, travel, equipment, etc.).
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Bank Statements: To cross-check your income and outgoings.
Other Income & Deductions:
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Bank Interest: Statements showing any interest earned on your savings.
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Dividends: Vouchers or summaries for any stocks or investments held outside an ISA.
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Pension Contributions: Records of personal contributions that might qualify for tax relief.
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Charitable Giving: Records of any Gift Aid donations.
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Student Loan: Statements showing repayments if you are paying them back through Self Assessment.
