Anyone who picked up new untaxed income during the 2025 to 2026 tax year — from a side hustle, a rental property, going self-employed, or the High Income Child Benefit Charge — has until 5 October 2026 to register for Self Assessment and tell HMRC they need to file a tax return.
With online platforms now passing seller data to HMRC and frozen thresholds pulling more people in, far more first-time filers are caught this year.
The dates that matter:
- 5 October 2026 — register for the 2025 to 2026 tax year, which ran from 6 April 2025 to 5 April 2026
- 31 October 2026 — deadline for a paper return
- 30 December 2026 — last date to ask HMRC to collect a bill under £3,000 through your PAYE tax code
- 31 January 2027 — online return, payment, and any first payment on account
- 31 July 2027 — second payment on account
Why more people are caught this year
HMRC now receives data straight from online platforms. Under the UK’s version of the OECD digital platform reporting rules — widely known as DAC7 — marketplaces including Vinted, eBay, Etsy, Depop, Airbnb, Uber and Deliveroo report seller information to HMRC where a seller makes 30 or more transactions or is paid more than €2,000 (around £1,700) in a calendar year.
The first reports, covering 2024, reached HMRC in early 2025, and the rules are now fully in force.
HMRC cross-checks that information against its own records, so someone who should have registered but has not is far more likely to be flagged.
Frozen allowances add to the pull: the personal allowance has been held at £12,570 and is now set to stay there until April 2031, so rising incomes tip more people over tax thresholds each year.
Who needs to register for Self Assessment
The groups HMRC expects to register for the 2025 to 2026 tax year include:
- sole traders and freelancers whose gross self-employment income passed £1,000, the trading allowance
- landlords with property income above £1,000, the property allowance
- members of a business partnership
- anyone with other untaxed income — dividends above the £500 allowance, savings interest, capital gains above the £3,000 exempt amount, or foreign income
- those liable to the High Income Child Benefit Charge, which applies where one partner’s adjusted net income tops £60,000
Myrtle Lloyd, HMRC’s Chief Customer Officer, has said in the department’s Self Assessment registration guidance: “If you are new to Self Assessment and unsure how the process works – HMRC is here to help. We have a wealth of resources and guidance available on GOV.UK to help customers register, sign up to the online services and complete their tax return.”
The £1,000 allowances — and why old clothes are usually fine
The two £1,000 allowances do a lot of work. The trading allowance means gross self-employment or casual income up to £1,000 a year does not need to be declared; the property allowance does the same for rental income. Cross either threshold and registration is generally needed.
Selling personal belongings second-hand — clearing out a wardrobe on Vinted, say — is not trading, even when a platform reports the sales to HMRC.
Someone selling used items for less than they paid generally has no income tax to pay, because there is no profit. Being named in a platform report is not the same as owing tax.
What has changed for directors and Child Benefit
Two changes are worth flagging for first-time filers. Directors of close companies who are also shareholders now have to give more detail on the 2025 to 2026 return — filed from 6 April 2026 — including the company’s details, the dividends taken from each close company, and the highest percentage shareholding held at any point in the year.
The extra boxes do not change the tax owed, but missing entries can prompt an HMRC query.
For Child Benefit, there is now an alternative to Self Assessment.
Since September 2025, employees who face the High Income Child Benefit Charge and have no other reason to file can choose to pay it through their PAYE tax code using a new digital service on GOV.UK — which can remove the need to register for Self Assessment in those cases.
What to do now
If any of this applies to you, here is how to get ahead of the deadline.
- Check whether you need to file. HMRC’s free “Check if you need to send a Self Assessment tax return” tool on GOV.UK only takes a few minutes and tells you where you stand.
- Register as early as you can. After you register, HMRC posts your Unique Taxpayer Reference (UTR), usually within 10 working days (21 days if you are abroad). You then sign up for the online service and wait for an activation code, sent within 7 working days (21 days abroad). Allow roughly three to four weeks from registering to being able to file — which is why leaving it until autumn is risky.
- Budget for payments on account. If your bill tops £1,000 and less than 80% of your tax was collected at source, HMRC asks for advance payments towards the next year — each 50% of the current bill. A first £3,000 bill can therefore become £4,500 due on 31 January 2027 (the bill plus a £1,500 first payment on account), with another £1,500 the following July. First-time filers are routinely caught out by this.
- File and pay by 31 January 2027. If your bill is under £3,000 and you would rather it came out of your salary, file by 30 December 2026 to ask HMRC to collect it through your tax code.
Filing is not only about a bill. Registering and submitting a return can also produce a refund — for instance where too much was deducted at source, or where allowable expenses have not been claimed.
The Tax Rebate Services guide to Self Assessment tax returns walks through the process and what can be claimed.
On penalties, the position can be more forgiving than many fear. Where tax is owed and someone registers after 5 October, the failure-to-notify penalty is based on the potential lost revenue and can run from 0% to 30% for a non-deliberate failure, rising higher for deliberate cases.
The Low Incomes Tax Reform Group points out that if you notify HMRC after 5 October yet pay your tax in full by 31 January, the failure-to-notify penalty should be nil.
Anyone who meets the criteria but turns out to owe no tax has no legal duty to notify by 5 October, and cannot be charged a failure-to-notify penalty for registering late — though HMRC still advises registering by then.
Late filing is treated separately: a £100 penalty applies as soon as the 31 January deadline passes, then £10 a day after three months up to £900, with further charges of 5% of the tax due or £300 (whichever is higher) at six and twelve months.
For free help, HMRC’s own guidance, the charity TaxAid, and the Low Incomes Tax Reform Group are good starting points.
Key Takeaways
- The deadline to register for Self Assessment for the 2025 to 2026 tax year is 5 October 2026; that year ran from 6 April 2025 to 5 April 2026.
- You are likely caught if you had untaxed income over £1,000 from self-employment or property, dividends over £500, taxable gains, or the High Income Child Benefit Charge.
- HMRC now receives seller data from platforms like Vinted and eBay, so unreported income is far easier to spot — but selling personal items at a loss usually is not taxable.
- Registering takes roughly three to four weeks end to end, so leaving it late risks missing the January filing window.
- If you owe tax but pay in full by 31 January 2027, the failure-to-notify penalty should be nil; filing can also mean a refund, not just a bill.
Written by:
Tax Rebate Services Editorial Team
Reviewed by:
Tony Shanks
,
qualified Taxation Technician (ATT)
Last updated:
This article provides general information and is correct as at the date shown. It isn't personalised tax advice — for help with your own circumstances, speak to a qualified adviser or HMRC.
