How to complete a self-assessment tax return

Putting off filling in your dreaded tax return? This complete guide takes you through the process step-by-step so can file your self-assessment tax return in just minutes. 

Our latest student money survey revealed that 8% of students make money through self-employment – and we’re constantly being inspired by students who make money by setting up their own unique businesses.

The independence of working for yourself is great and there’s the potential for big money, but it does mean you have to take responsibility for your own taxes – and that means submitting a self-assessment tax return every January.

It can seem like a daunting task that will take you hours, but our guide will help make the process as quick and painless as possible (and will help you avoid paying any penalties).

Do you need to do a self-assessment tax return?

Most people get their income tax automatically deducted from their wage each month so they don’t need to worry about it – unless you overpay, in which case you could be due a refund.

But if you make money in other ways (for example, from freelance work or running your own business) you’ll have to complete a self-assessment tax return to tell HMRC how much you’ve earned and therefore how much tax you owe.

You need to complete a self-assessment tax return if you’re:

Other income streams required in a self-assessment tax return include:

How to submit a HMRC tax return

  1. Register with HMRC

    First things first: you’ll need to register yourself as either self-employed, not self-employed (but earning untaxed income) or as a partner in a business partnership.

    If you’ve submitted a tax return before, but didn’t send one for the last tax year, you’ll probably have to re-register.

    Once you’ve registered you’ll receive a Unique Taxpayer Reference (UTR) and an account for the Self Assessment online service, which you use to complete your tax return and pay your tax.

    You’ll be sent a code in the post within 10 working days which you’ll need to use to activate your account online within 28 days of receiving it.

    Remember that the deadline for registering is earlier than the deadline for completing your tax return – check the latest deadline dates below.

  2. Submit your tax return

    First of all you should gather together all the information you need to be able to complete your tax return. This includes your National Insurance Number, your Unique Taxpayer Reference, bank statements showing your income and interest statements from your savings.

    On that note, make sure to keep a hold of all receipts and statements, and don’t throw them away once you’ve submitted your tax return. You can be asked to submit things up to six years later, and it can be a nightmare if you don’t have them to hand.

    You can complete your tax return by filling out a paper form or completing it online, but if you choose the paper option make sure you send it off in plenty of time to meet the deadline.

    The form can seem really daunting but bear in mind that you only need to fill in the parts that are relevant to you and your situation.

    In fact, if you’re doing it online the form will automatically respond to your answers and remove sections that don’t apply to you. What’s more, you can save and come back at any time if you can’t stomach it all in one go.

    Remember that you have to report all the income you’ve earned in the previous tax year (April to April). HMRC have loads of advice and guidance to direct you through the form and show you where all the relevant information goes.

    If you’re earning over the student loan repayment threshold (£25,725 a year), you’ll also have to factor in your student loan repayments. Make sure to make a note of any student loan repayments you’ve already made through any jobs you’ve had that tax year, or else you could end up overpaying.

  3. Pay your tax to HMRC

    This is where things start to get real – it’s time to pay your tax! How much tax you owe depends on the income tax band you’re in, and HMRC will calculate this based on what you declare in your self-assessment form.

    Paying tax this way can be tricky to budget, and having a big lump sum of tax taken out of your account at once could leave you feeling the pinch. Also don’t forget to accommodate for National Insurance contributions, as this forms part of your tax calculations.

    It’s best to set aside some money regularly throughout the year for this purpose, or you could set up a budget payment plan to pay your tax in regular instalments throughout the year instead.

    The deadline for paying your tax is the same date as the deadline for submitting your tax return: the 31st January of the year after the tax year. In other words, for the tax year of April 2017 – April 2018, the deadline for submitting your return is the 31st January 2019.

    If the deadline falls on a weekend or bank holiday, make sure your payment reaches HMRC on the last working day before this (unless you’re paying by Faster Payment or debit/credit card).

    There are loads of different ways to pay but bear in mind that some methods take longer than others, so you’ll have to account for this to ensure you don’t miss the deadline (and face a penalty).

    Same or next day tax payment

    – Online or telephone banking (Faster Payments)
    – CHAPS (Clearing House Automated Payment System)
    – Debit or corporate credit card online
    – At your bank or building society (you’ll need a paying-in slip from HMRC for this)

    Three working days

    – BACS
    – Direct debit (if you’ve set one up with HMRC before)
    – By cheque through the post

    Five working days

    – Direct debit (if you’ve not set one up with HMRC before)

    Once you’ve paid, check your HMRC online account to ensure the payment has gone through – it will take three to six working days to show as paid.

Tax return deadlines

It’s your responsibility to submit your tax return by the deadline, which is always:

But don’t forget you can submit your tax return anytime from the end of the tax year (5th April 2019 for the 2018/19 tax year).

The deadline for registering for self-assessment is earlier, so don’t leave it to the last minute!

Tax return deadlines 2019

If you miss the deadline, you’ll have to pay a hefty penalty so get that date in your diary and make sure you don’t forget!

Payments on account

Payments on account are essentially advance payments towards your tax bill – helping to spread the load across the year instead of paying it all in one lump sum.

You make two payments on account a year, unless your last self-assessment tax bill was less than £1,000 or you’ve already paid over 80% of the tax you owe.

Each payment is half of your previous year’s tax bill, and they’re due by midnight on 31st January and 31st July. If you still have tax left to pay after these advance payments, you pay the remainder by midnight on 31st January the following year.

Example: Your tax bill for the 2017/18 tax year is £5,000. The previous year you made two payments on account of £2,000 each. This means that by 31st January 2019 you have to pay £3,500. This includes the £1,000 remaining balance for your 2017/18 tax bill and your first payment on account for your 2018/19 tax bill (£2,500).

Note that payments on account do not include anything you owe for student loans.

What happens if you miss the tax return deadline?

If you miss the tax return deadline you’ll have to pay a penalty, which is £100 if you’re up to three months late. You’ll be charged an even higher fee if you’re later than three months, with interest on top – so don’t miss it!

In some circumstances, you can appeal a penalty if you have a reasonable excuse for missing the deadline, but you should never rely on this appeal being successful.

Excuses that may prove successful include the recent death of a partner or an unexpectedly long stay in hospital, but they’re assessed on a case-by-case basis.

Tax isn’t as scary as it seems once you get to grips with it – clue yourself up with our seven basic tax facts everyone should know!