If you’ve figured out that you do need to file a Self Assessment tax return, your very first job is to register with HMRC. This is how you get your Unique Taxpayer Reference (commonly referred to as your UTR) and without that little 10-digit number, you won’t be able to submit a return at all.
The good news? Registering isn’t as daunting as it seems. Here’s exactly what to do, how long it takes, and a few things to watch out for along the way.
What’s a UTR, and Why Does HMRC Love It So Much?
Your UTR (Unique Taxpayer Reference) is basically your ID number for the Self Assessment system. It’s what HMRC uses to match your tax return to you.
You’ll need it for:
filing your tax return
checking your tax bill
talking to HMRC
appointing an accountant
If you’re filing a tax return for the first time, you won’t have one yet, but HMRC will issue it as soon as you’re registered.
When Should You Register for Self Assessment?
There’s an official HMRC deadline: The 5th of October following the end of the tax year when you started earning taxable income.
If you leave registration until December or January, things slow down. Mail gets delayed. Activation codes arrive late. Stress levels rise. Registering early gives you some breathing room to get things sorted.
Who Actually Needs to Register?
You’ll need to register if you:
earned more than £1,000 from self-employment
have income that isn’t taxed through PAYE
earn rental, dividend or investment income
earn over £100,000
need to pay the High Income Child Benefit Charge
received a notice from HMRC to file
If you’re still unsure, our earlier guide breaks it down in plain English: Do I Need to File a Self Assessment Tax Return? UK Rules Explained.
How to Register for Self Assessment (Step-by-Step)
Step 1: Sign into (or set up) your Government Gateway
If you’ve already got a Government Gateway login, great! You’re halfway there. If not, HMRC will ask you to create one using:
your email
your name
a password
identity verification (passport, licence, or credit check)
It’s quick, although the verification step sometimes takes a couple of minutes.
Step 2: Tell HMRC why you’re registering
You’ll be asked what applies to you. The most common options are:
Self-employed / sole trader
Not self-employed but still need to file (e.g. rental income)
Partner in a partnership
Step 3: Fill in your details
HMRC will ask for your:
full name
National Insurance number
date of birth
current address
any business name
the date you started earning self-employed income (if relevant)
Once that’s submitted, you’re officially in the queue for a UTR.
Step 4: Wait for your UTR to arrive in the post
HMRC will send your UTR to your home address. Most of the time it arrives in 7–10 working days, but it can take longer in December and January when demand spikes.
So if you’re planning to file soon… register sooner rather than later.
Step 5: Activate your Self Assessment account
Along with your UTR, HMRC will send an activation code. Pop this into your Government Gateway account and, just like that, your Self Assessment account is live. After that, you’ll be able to:
file your tax return
check your tax bill
update your details
appoint an accountant
How Long Does it Really Take to Get a UTR?
Officially: 7–10 working days.
During busy season: 2–3 weeks (and sometimes longer).
If you’re hoping to get your return filed before the January deadline, don’t leave this step to the last minute.
Common Registration Hiccups (And How to Avoid Them)
Address issues
If HMRC holds an old address, your UTR will go there, and you’ll be waiting a long time. Make sure your details are up to date first.
Identity checks failing
If your personal details don’t match HMRC’s records exactly, the system can reject them.
Registering too late
This is the big one. Many people register in January, only to find their UTR won’t arrive until February. At that point, HMRC penalties are unavoidable.
Need a Hand Getting Everything Set Up?
Registering is just the first hurdle. Once your UTR arrives, you’ll still need to:
organise your income and expenses
keep the right records
calculate your tax
submit the return
pay what you owe
If you’d rather skip the stress, our team at Platinum Accountancy Services can help you get everything sorted, from your initial registration all the way through to filing your return.
We also offer bookkeeping and personal tax services, which make it far easier to stay organised throughout the year (and avoid last-minute panic next January!).
And if you’d like some help getting started, just get in touch, we’re always happy to guide you through it.
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