Self Assessment Deadlines: What happens if I haven’t registered?

You found out you have to do a self assessment but the deadline to register has passed. What happens when you don’t register for Self Assessment in time? Can HMRC immediately start charging you penalties?

If you became self-employed, made sizeable gains on shares or cryptoassets, became an LLP member or earned a six-figure salary between 6 April 2021 and 5 April 2022, then you may well have needed to register for Self Assessment. The problem is that HMRC’s guidance on deadlines says you need to have registered for Self Assessment for the 2021-22 tax year by 5 October 2022 – around three and a half months ago.

So, if you’ve missed this deadline, how do you go about fixing it? Well, you should still register as soon as you can because you still need to submit a tax return eventually. HMRC grant all new Self Assessment sign-ups a three-month submission window from the date of registration (extending beyond the default 31 January deadline) so you won’t get stung with penalties right off the bat, but the clock does start ticking and you will still be due to pay interest on any payments made after the end of January.

Once registered, you’ll be sent your Unique Taxpayer Reference. This is similar to a National Insurance Number because it’s specific to you, but is only used for Self Assessment purposes. With this, you or your accountant can now draft up your tax return and figure out how much tax you’re due to pay. If your tax bill is higher than anticipated, and you’re unsure whether you’ll be able to pay your tax bill in one go, HMRC may allow you to pay in instalments if you are registered and submit your tax return before 1 April – another great reason to get registered sooner rather than later.

And if you’re not certain whether you need to register, HMRC’s guidelines for Self Assessment registration can be found here, so don’t get caught out.

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ben crampin


Ben’s been here pretty much since the get-go and, as such, has been instrumental in growing the business into what it is today.
He’s passionate about, in his words, ‘helping people and businesses that are just constantly being taken advantage of’ by providing affordable advice and support with an eye to ‘levelling the playing field’.
Ben looks forward to the day when automation will, once and for all, fumigate the fear and confusion caused by oppressive bureaucracy and strongly believes that ‘technology holds the solutions to the problems we’re trying to solve’.
Furthermore, he can see that technology will, in time, provide the scalability required to help a theoretically limitless number of SMEs survive and thrive against the odds.
Ben doesn’t think much of government agencies and he doesn’t suffer fools; two points that aren’t always mutually exclusive.