Started Self-Employment or Renting Out a Property This Year? Register for Self Assessment by 5 October
A deadline that catches a lot of people out
Every year, HMRC reminds people that if they became newly self-employed, started letting out a property, or picked up a new source of taxable income during the last tax year, they need to register for Self Assessment by 5 October following the end of that tax year. For income earned between 6 April 2025 and 5 April 2026, that deadline falls on 5 October 2026.
It's an easy one to miss, because there's no big headline moment attached to it — no filing, no payment due that day, just a quiet administrative step. But skipping it can leave you scrambling later, so it's worth checking now whether it applies to you.
Who needs to register
You'll usually need to register for Self Assessment by 5 October 2026 if, at any point during the 2025/26 tax year, you:
Became self-employed or started freelancing, and earned more than £1,000 from it
Started renting out a property for the first time, including a first buy-to-let or a room let above the Rent a Room threshold
Became a partner in a business partnership
Began regularly selling goods or services online with a view to making a profit, rather than simply clearing out unwanted possessions
Had other new untaxed income that isn't collected through PAYE
The key phrase HMRC uses is that you haven't previously told them about this income and haven't already been sent a tax return covering it. If you've registered and filed before for the same type of income, you don't need to register again.
Why online sellers should pay particular attention this year
Anyone using platforms like eBay, Vinted, Etsy or Airbnb has probably noticed these platforms now share seller data directly with HMRC as a matter of course. That doesn't change the underlying rules — the £1,000 trading allowance still means genuinely casual selling stays outside Self Assessment — but it does mean HMRC has much better visibility of who's trading regularly for profit. If that's you, and 2025/26 was the year it tipped from hobby into something more consistent, this is the deadline that starts the clock.
Landlords letting a property for the first time are in a similar position: rental income needs registering and reporting from year one, even if the amount involved feels modest.
What happens if you miss it
Missing the 5 October registration deadline doesn't automatically mean a penalty — but it does put you at risk of one for “failure to notify” if tax ends up being paid late as a result. Practically, HMRC can also take a while to process a late registration, and you still need a Unique Taxpayer Reference (UTR) before you can file anything. The UTR and activation code typically arrive by post and can take around 10 working days (longer if you're abroad), so leaving it right up against the 31 January 2027 filing and payment deadline gives you very little room if anything goes wrong.
How to register
Registration is done through gov.uk, and the process is slightly different depending on whether you're registering as newly self-employed, as a partner, or for other income (such as rental income) without being self-employed. In each case, once you're set up you'll need to file online by 31 January 2027 (or 31 October 2026 if filing on paper), and pay any tax owed by 31 January 2027.
If you're not sure which category applies to you, or whether your situation this year actually crosses into Self Assessment territory, it's worth checking sooner rather than later — the registration itself takes only a few minutes, but getting the UTR sorted in good time takes the pressure off everything that follows.
We're here to help
If you're based in Bury or elsewhere in Greater Manchester and you're not sure whether you need to register — whether it's a new letting, a side hustle that's grown into something more, or your first year of self-employment — Jackson Lee Accountants can help you work it out and get registered correctly. It's far easier to sort this now than to untangle it in January.
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