Filing your first tax return? Time is running out to get your UTR number

The tax return deadline is approaching fast - and today could be the final day that you can register for a UTR number and still file on time.

HMRC states that it can take up to 10 working days to receive your UTR number, and you'll then have to wait up to an additional 10 working days to receive an activation code.

You need both codes to log into your Government Gateway account to send your online tax return, which is due on 31 January.

If you've sent a self-assessment tax return in previous years, you'll already have a UTR number assigned to you and won't need to register for a new one.

Which? explains what a UTR number is and who needs to register for one.

What is a UTR number?

A UTR number is a 'unique taxpayer reference' number used by HMRC to track the tax records of anyone who registers for self-assessment. The number is 10 digits long, and sometimes has a letter 'K' at the end.

Much like a National Insurance number, once you register for a UTR number, it stays with you for the rest of your life.

If you're submitting a tax-return for the first time, you'll need to register with HMRC as soon as possible. Technically the deadline to do was 5 October 2018, assuming your taxes were incurred in the 2017-18 tax year. But ifyou've not registered already - don't panic. Go to HMRC's website and sign up foran accounttoday.

Alternatively, you can print off the form and send it in the post - although keep in mind that sending the form in the post will take much longer, and probably won't arrive in time for you to meet the 31 January deadline.

Applying for a UTR any later than today means you may run out of time. HMRC urged people who are likely to face difficulties meeting the deadline to contact them as early as possible.

• Find out more:online tax returns

Do I need a UTR?

You'll only need a UTR number if you're required to submit a self-assessment tax return. There's a wide range of situations where you might need to do this - for example, if you rent out a property, make a capital gain or run your own business, you'll have to fill out a return.

If you're not sure whether or not you need to pay self-assessment tax, our guide Who should submit a tax return? can help to explain.

If all of your income is earned through employment, you won't need to register for a UTR number or submit a self-assessment tax return, as you'll already have paid income tax and National Insurance contributions before receiving your salary.

• If you need a hand filing your return, you can use the Which? tax calculator to tot up your bill and submit direct to HMRC.

What if I've lost my UTR number?

If you've already been given a UTR number and you've lost it, you don't have to register for a new one.

You'll be able to find it on a previous tax return or other documents you've received from HMRC, such as notices to file a return, payment reminders and in your HMRC online account.

The UTR number may also be labelled 'tax reference' or 'Official Use' on forms.

If you still can't find your UTR number, you can call HMRC's self-assessment helpline on 0300 200 3310. It's helpful to have your NI number to hand when you make the call.

In some cases, your UTR may become dormant if you stop needing to submit a tax return - but don't worry, as it will automatically be reactivated when you next pay self-assessment tax.

Can I submit a tax return without my UTR number?

The first time you pay by self-assessment, you must have a UTR number.

After you've registered, you can submit a paper tax return in following years without specifying your UTR number. However, the deadline for filing a paper tax return has passed - so if you submit one now, you could receive a fine for late submission.

You could also receive a fine if you submit a tax return with the wrong UTR number. This is one of the most common mistakes made on tax returns every year.

Therefore, it's best to contact HMRC to track down your UTR number before submitting your return.

What if I miss the tax return deadline?

The final deadline to submit your 2017/18 tax return is 31 January, but this applies to online returns only. The paper tax return deadline was 31 October 2018, so if you still haven't submitted a tax return, your only option is to do so online.

Missing the deadline means you could incur a fine from HMRC.

You'll be fined if you're even just one day late, and the fines will increase for each subsequent day after that, as shown below:

• Find out more:late tax returns and penalties for mistakes

Submit your 2017/18 tax return with Which?

For an easy-to-use, jargon-free way to file your tax this year, use theWhich? tax calculator.

Tot up your tax bill, get tips on where to save and submit your return direct to HMRC with Which?.