How to Fill In Your HMRC Tax Return

In this step-by-step guide, you’ll find everything you need to know to fill in your tax return online, one of the most important self assessment forms when you become self-employed to help you beat the HMRC deadline.

Not sure whether you need to fill in a tax return? Use this guide to help you work out whether you need to send one to HMRC or not.


1. When is Your HMRC Tax Return Due?

The deadline for filing your tax return online is 31 January, following the end of the tax year. A tax year runs from 6 April to 5 April. So your 2019/2020 self assessment form return is due by 31 January 2021.

There are strict penalties for failing to file your tax return on time, which increase the longer you leave it and even though may be able to appeal against penalties if you have a reasonable excuse, HMRC isn’t very generous with what they consider reasonable.

You can choose to complete a paper tax return instead of doing it online, but you’ll get this into HMRC earlier, by the end of October. And if you want to pay any tax you owe through your PAYE code, the deadline is the end of December so leave enough time to make arrangements to change your tax code.

1.2 Will HMRC Send Me a Tax Return?

HMRC won’t send you a tax return (also known as an SA100) because, for a majority of individuals, it needs to be completed online. Instead, once the tax year comes to an end, you’ll be able to find access to your tax return by going online and looking in your .GOV tax account.

2. How Early Can You Complete Your Tax Return?

You can send in your tax return at any time once the tax year ends, but don’t worry you won’t need to pay your tax until the 31 January. Some people prefer to get it done as soon as possible so they have plenty of time to fill in their tax return or they know they are due a tax refund and want to get the money back.

3. Where to Find Your Tax Return

You tax return will appear in your .GOV account automatically once you have registered as self-employed. You can login via your personal tax account to find it, here’s what to do if you’ve lost your user ID or password

4. What You Need Before You Get Started Completing Your Tax Return

Getting all the documents you need ready in advance will make completing your HMRC tax return quicker and easier. You’ll only need documents that are relevant to the tax year you are filing your return for. Here’s a list of the things that you may need:

  • Personal details including your UTR number, national insurance number and bank details if you are expecting a tax refund;
  • Partners Information if you want to claim marriage allowance;
  • Employment Information;
  • P45 or P60 if you were employed either full-time or part-time during the year;
  • P11d if you were employed and received a taxable benefit like private medical insurance or a company car;
  • Dividend certificates;
  • Bank interest certificates;
  • Student loan statements;
  • Pension statements and pension contributions;
  • Self-employment income and expenses from your accounts;
  • Rental income and expenses including managing agents statements, details of allowable expenses and mortgage statements;
  • Previous years tax return and details of any tax losses;
  • Details of any other income you’ve received.

More Help: Do I Need to Show Bank Interest On My Tax Return?

5. How to Fill in Your Tax Return Online

5.1 Tell Us About You

You’ll need to start completing your return by filling out the “Tell Us About You” section. This section is your chance to check HMRC have the right personal information about you and for you make any corrections necessary, like a change of address. It will be pre-populated if HMRC has any of the information on their system already, but it still pays to check that everything is correct.

Some boxes like phone number and email address are optional, so it is up to you whether you want to provide it. But it can be useful to add them in case HMRC need to contact you. Make sure that you:

  • Check all your personal details;
  • Ensure the box is ticked to say you are UK Resident;
  • Tick the box if you are entitled to blind person’s allowance;
  • Enter information if you are making student loan repayments, the type of plan you are on and whether you are employed or self-employed.

Once completed you’ll move onto the tailor your return section where you tell HMRC about your different earnings and remove any sections of the tax return that are not relevant to you.

5.2 Tailor Your Return

You’ll need to work your way through confirming what types of income you have received for example self-employment or dividends and the income tax reliefs you’ll planning to claim to reduce your tax bill.

Once you have tailored your online tax return to your personal circumstances, it’s time to start inputting the numbers. You’ll notice that many of the sections have a cross next to it, the aim to get all ticks.

More Help: How to Complete the Tailor Your Return Section

5.3 Employment Page

If you were employed you’ll need to enter your income from your P45 or P60, completing more than one employment section if you had more than one employer during the tax year. You’ll also be able to claim tax relief on expenses that you paid for but were not reimbursed by your employer for example if you had to work from home due to the coronavirus pandemic.

If you own a Limited Company and were on the payroll, then you’ll also need to include details of this employment here too.

More Help: How to Complete the Employment Section of Your Tax Return

5.4 Self-Employment Section

You’ll be presented with the self-employment section if you have become self employed, are a sub-contractor under the CIS scheme or a registered foster carer.

The first thing you’ll need to do is calculate your business turnover because if it is less than £85,000 then you’ll be able to complete the short-form self-employment section, which requires less information.

Next, you’ll need to have your business expenses ready and then decide what tax reliefs like capital allowances and loss reliefs you want to claim.

More Help: How to Complete The Self-Employment Section of Your Tax Return

5.5 Self-Assessment for the High-Income Child Benefit Charge

If you or your partner earn between £50,000 and £60,000, including through self-employment, then you’ll need to pay back any child benefit you have received in the form of an income tax payment. You can choose to do this by electing to stop receiving child benefit payments or paying the high-income tax charge by filling out an HMRC tax return.

This charge claws back child benefits paid at a rate of 1% for every £100 you earn over £50,000. That means once your income reaches £60,000 you will not receive any child benefit.

More Help: How to Fill In Your Tax Return for the High Income Child Benefit Charge

6. Paying Your Tax Bill

You can pay your self-assessment tax bill online in a variety of ways including by direct debit, bank transfer and with a debit card. If you want to pay by bank transfer, then you’ll find the bank details on the HMRC website.

Whichever method you choose, make sure you use your UTR number as the reference for your payment so it gets allocated to your account correctly.

Alternatively, if your tax bill is less than £3,000 and you are employed, you can choose to pay your self-assessment bill through your PAYE code but you must have submitted your tax return by 30 December.

If you can’t pay your tax bill, then you should know that HMRC takes non-payment really seriously and has the power to make you bankrupt if needs be and add penalties which escalate. That being said, they will work with you if you are struggling to pay your tax bill.

First of all, you MUST file your tax return in January. If you don’t you’ll face penalties until you do which only increase your debt. Once you know how much tax you own, CONTACT HMRC. You can do this online or by phone and it means you can agree on a suitable repayment plan. By sorting out a repayment plan, it means you’ll freeze penalties and interest that will only mean you end up owing HMRC even more money.⁠

7. Filling in a Paper Tax Return

You can get a paper tax return form by:

  • Downloading it online;
  • Calling HMRC on 0300 200 3310 and asking them to send you a return.

If you are eligible to file a short form tax return (a simplified version of the form) then HMRC will send this to you. You cannot download it or request one.

Don’t forget if you choose to file a paper tax return it is due by 5 October.

8. What Happens if You Miss the Filing Deadline

If you miss the HMRC self-assessment tax return deadline, HMRC will issue automatic penalties. You may be able to have these reversed if you have a reasonable excuse.

These start at an immediate £100, rising the longer you leave it. There will also be interest charged on any late payments of tax.

9. Getting a Tax Refund After Submitting Your Tax Return to HMRC

If you are due a tax refund, you’ll need to let HMRC know that you want a repayment and enter your bank details. Once this is done, it can take up to 4 weeks for HMRC to process your refund and send it back to you.

10. Contacting HMRC about Your Tax Return

If you have a question for HMRC about registering or the self-assessment then contact HMRC on 0300 200 3310.

About Anita Forrest

Anita Forrest is a Chartered Accountant, spreadsheet geek, money nerd and creator of www.goselfemployed.co - the UK small business finance blog for the self-employed community. Here she shares simple, straight-forward guides to make self-employment topics like taxes, bookkeeping and banking easy to understand.