Filing your first tax return? You need a UTR number and time is running out

If you need to submit a tax return for the first time but haven't yet registered for self-assessment, time is getting tight. In fact, if you don't register by tomorrow, you'll be in danger of missing the 31 January deadline.

First-time filers need a 'unique taxpayer reference' or UTR number in order to submit a self-assessment tax return, but it can take time to get one. HMRC says it can take up to 10 working days to receive your UTR number and a further seven working days to receive an activation code.

Both these numbers are required to log into your Government Gateway account, where you'll need to fill out and send your online tax return.

HMRC's latest figures show that almost half of those due to submit a tax return are still yet to do so; of the 11.7m tax returns HMRC is expecting to receive, 5.4m returns are still outstanding. Anyone who misses the deadline could receive a hefty fine.

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

Here, we explain what a UTR number is, and who needs to register for one.

What is a UTR number?

A UTR number is issued by HMRC to track the tax records of anyone who registers for self-assessment.

It's 10 digits long and sometimes has a letter 'K' at the end.

Your UTR number is personal to you and stays with you throughout your life - much like a National Insurance number.

When submitting a tax return for the first time, you should register with HMRC as soon as possible to let them know to expect your tax return.

Technically, the registration deadline was 5 October 2019 to declare income for the 2018-19 tax year. But if you haven't already registered, you can still go to HMRC's website and sign up for an account.

There's also the option to apply over the phone on 0300 200 3310. Alternatively, you could write to HMRC to request a UTR number - but this option is likely to take a while, so you might not get set up in time to meet the deadline.

• Find out more:what is a UTR number?

What if I've lost my UTR number?

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

It will be printed on any previous tax returns or other documents you've received from HMRC - such as notice to file a return and payment reminders. It should also be recorded in your HMRC online account.

The UTR number can sometimes be labelled as a '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 to help track down your information.

UTR numbers can become dormant in cases where you stopped needing to submit a tax return for several years. In this case, it should automatically be activated the next time you submit a return.

Can I submit a tax return without a UTR number?

Those submitting a self-assessment tax return for the first time will definitely need a UTR number.

If you can't track down your UTR number, don't try to guess it as getting it wrong could result in a fine.

HMRC can fine you if it thinks your tax return has been filled out carelessly, and incorrect UTR numbers are one of the most common mistakes made each year.

If you're not sure what your UTR number is, contact HMRC.

• Find out more:how to fill in a self-assessment tax return

What if I miss the tax return deadline?

HMRC must receive your online tax return by midnight on 31 January. If you miss the deadline, you could automatically be charged £100 - even if you're just a few minutes late.

If you're more than a day late, the penalties can increase - as outlined below:

Late payment charges

If you miss the 31 January deadline for submitting your tax return, you'll also miss the payment deadline - which is also on 31 January.

Late payment charges are in addition to fines for late submissions.

You'll be charged interest (currently 3.25%) from 31 January. If you still haven't paid after 30 days, you'll be charged an extra 5% of the tax due, after six months there'll be a further 5% charge, and after 12 months there's another additional 5% charge.

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

Submit your 2018-19 tax return with Which?

For an easy-to-use, jargon-free way to file your tax return this year, try the Which? tax calculator.

You can tot up your tax bill, get tips on how to make savings and submit your return direct to HMRC with Which?.