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The 5 October Self Assessment registration deadline

Cameron Pitchford
September 24th, 2026

If you became self-employed, started a side hustle, or began renting out a property for the first time during the 2025/26 tax year (6 April 2025 to 5 April 2026) and you haven’t yet registered for Self Assessment, the clock is ticking. HMRC’s deadline to notify them of new, previously undeclared income is 5 October following the end of the tax year in question — which this year falls on Monday 5 October 2026.

This one catches a lot of people out, particularly those who’ve picked up freelance work, started an Etsy shop, or begun letting out a spare room or second property without quite thinking of it as “a business.” The registration deadline is separate from the filing and payment deadlines (31 January for online returns), but missing it can still land you with a “failure to notify” penalty on top of whatever tax is eventually due — even if you go on to file and pay on time once you are registered.

If any of this sounds like it might apply to you, or to someone you know who’s recently gone self-employed, get in touch and we’ll get the registration sorted before the deadline.

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