Guide to filing your HMRC Self Assessment tax return

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If you’ve ever wondered: ‘How do I complete my HMRC Self Assessment?’ you’re in the right place. On this page, we’ll discuss what a Self Assessment tax return is and explain the step-by-step process to completing yours.

To begin with, what is a Self Assessment tax return in the UK? Also known as an income tax return, this is a form you submit to HMRC that reports your income and any relevant expenses or tax reliefs you’re eligible for in a given tax year (which runs from 6 April to 5 April). Not everyone needs to complete a Self Assessment tax return.

Yes, HMRC can and does check your income in your Self Assessment tax return. They have various ways of doing this, including:

• Data matching - HMRC receives data from a number of sources, including employers and pension providers (via PAYE), and banks and building societies (regarding interest earned)

• Connect - HMRC uses a system called Connect, which cross-references data from other UK government databases, including DWP and Companies House

• Random investigations - HMRC may randomly investigate people who work in certain industries and/or have inconsistent or incomplete tax records

No, not everyone needs to complete a HMRC Self Assessment tax return. You may need to file one if you’re self-employed, a company director, or receiving untaxed income (for example, rental income). If you’re not sure, you can check whether you need to complete a tax return.

You can do your taxes by completing your Self Assessment tax return and submitting it to HMRC before 31 January. You can do this online or by sending the SA100 paper version.

If it’s your first time filing an HMRC tax return, you’ll have to register for Self Assessment on the gov.uk website first. You’ll need to do this before 5 October, after the end of the tax year.

Take some time to gather any information you’ll need. This could include your National Insurance number, employment income, information about interest on savings, rental income, and any benefits you’ve been eligible for, for example, child benefit.

Log in to the HMRC website using your Government Gateway details and choose the relevant tax year.

Your HMRC Self Assessment form will be tailored based on your income and situation, so you’ll only be shown the sections you need to fill in. These might be: 

• Employment information

• Self-employment information

• Rental income

• Interest and dividends

• Any other income, for example, one-off payments or freelance work that isn’t part of your main business

• Expenses and reliefs, for example, business expenses, charity donations, and pensions

Once you’ve submitted all the relevant information, HMRC will calculate how much tax you owe. At this point, you’ll simply need to review your form and submit it. You’ll receive a submission receipt, your tax bill, and the relevant deadlines for payment.

Now that you’ve completed your HMRC Self Assessment return, it’s time for the most important part - you’ll need to pay your tax bill. The deadline for this is 31 January, but you may also need to make what’s known as Payments on Account if your bill is over £1,000. 

Completing your HMRC Self Assessment tax return if you are self-employed is the same process as it is for anyone else completing their Self Assessment. You’ll need to follow the steps above and ensure you check the relevant dates and deadlines for submission.

If you’re self-employed, it’s important to maintain good record-keeping through the tax year, keeping track of things like total income, business expenses, invoices, and receipts, so that you’re prepared when it comes to completing your HMRC Self Assessment.

Yes, you can complete your own HMRC Self Assessment tax return, and many people do so without the help of an accountant. There are guides on the gov.uk website to help you if you get stuck. 

However, if you have multiple income streams, earned capital gains in the tax year, have a high income (more than £100,000 a year), and/or have a complex tax situation, you may find it helpful to use an accountant for your HMRC tax return.

In short, it depends. Whether you get a tax refund automatically or not depends on how your tax is paid and how the overpayment happened. 

Tax refunds tend to happen automatically if you’re employed and pay tax through PAYE. You may be due a refund if you changed jobs mid-year, worked part of the year, or didn’t use your full personal allowance. In this case, HMRC will either send you a cheque or ask you to claim your refund online. 

However, if you’ve filed a Self Assessment tax return, HMRC won’t automatically process a refund. In many cases, you’ll need to log in to your HMRC account to claim it, or confirm how you’d like it handled - you can usually choose whether you want the refund to be sent to your bank account or held towards next year’s tax.

Automatic refunds can take anywhere from five days up to eight weeks after the tax year ends on 5 April. Self Assessment refunds are usually paid once the tax return has been processed, and it can be quicker if you claim via your online tax return.

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