Most Self Assessment deadlines are about filing or paying. This one’s different. It’s about whether HMRC even knows you need to file at all.
If you’ve had new income this tax year that HMRC doesn’t already know about, you may need to register for Self Assessment by 5 October, or risk a penalty for notifying them late, even if you’d have owed little or no extra tax. It’s one of the easier deadlines to miss entirely, precisely because it applies to people who don’t think of themselves as needing to do a tax return.
Here’s who it actually affects, and how to know if it’s you.
Why this deadline is different
Most people who complete Self Assessment already know they need to, because they did it last year too. This deadline exists for people it hasn’t caught up with yet: anyone with a new source of income this tax year that means they need to start filing, even though they haven’t had to before.
HMRC doesn’t automatically know about every source of income you receive. Employment income, taxed through PAYE, is reported to them directly. Plenty of other income isn’t, and it’s your responsibility to tell HMRC it exists, by registering for Self Assessment, if you haven’t already.
Common situations that trigger registration
There’s no single test that covers every case, but a few situations come up again and again:
Side income alongside employment. Freelance work, consultancy, selling goods regularly, or any other self-employed income earned alongside a main job. If it’s more than a one-off, and above the relevant trading allowance, it likely needs declaring.
Rental income. If you’ve started renting out a property this tax year, whether that’s a single room or a full second property, that income generally needs to be reported, even if the profit after expenses is modest.
Crypto gains. Selling, swapping, or otherwise disposing of cryptoassets can create a taxable gain, and a growing number of people are catching up with this only once HMRC’s data-sharing with exchanges flags it for them, rather than realising at the time.
Dividends over the allowance. If you’ve received dividend income, from your own company or investments, above the tax-free dividend allowance, that generally needs declaring too.
Becoming self-employed generally. If you started working for yourself this tax year in any capacity, registration is likely required regardless of how modest the income currently is.
None of these situations are unusual or obscure. That’s exactly why this deadline catches so many people out. Most of the income involved doesn’t feel like “the kind of thing you’d need to tell HMRC about,” until it turns out it was.
What happens if you miss it
Missing the 5 October registration deadline doesn’t necessarily mean a large tax bill. It can mean a penalty for failing to notify HMRC of your liability on time, calculated based on the tax that was ultimately due and how late the notification was, separate from any penalty for late filing or late payment further down the line.
In practice, this means someone with a fairly small amount of extra income can still end up facing a penalty that feels disproportionate to the tax actually owed, purely because the registration step was missed. It’s a deadline that rewards simply knowing it exists.
What to do if you’re not sure
If any of the situations above sound like they might apply to you this tax year, the safest approach is to check rather than assume it’s fine. Registration itself is a straightforward process, and doing it slightly earlier than necessary carries no downside. Missing it, even by a small margin, can mean a penalty that a five-minute check would have avoided entirely.
If you’re already confident you don’t have any new income sources this year, this deadline simply doesn’t apply to you, and there’s nothing further to do. The point isn’t to worry everyone unnecessarily. It’s to make sure the people who do need to act, often without realising it, don’t miss a deadline they didn’t know existed.
Final Thought
A quote from our Principal, Sunil Aggarwal:
“This is one of the only deadlines where the people most at risk are the ones who don’t think it applies to them.
If you’ve had any new income this year and you’re not sure whether it counts, that uncertainty is exactly the reason to check. It takes five minutes. Missing it doesn’t.”
If you’ve had any new income this tax year and you’re not sure whether you need to register, get in touch and we’ll give you a straight answer.
Not sure if this is you? Get in touch with DRS and we’ll help you work out whether registration applies before the 5 October deadline.
- Email: info@drs-tax.com
- Telephone: 020 8059 1891
- Or submit an enquiry via our Contact Us page