What happens after I file my Self Assessment tax return?

After filing your Self Assessment, you may have to pay a tax liability or you may be due a tax refund. Here, we outline what may be required of you.

Arjun Kumar
Arjun Kumar
Apr 3, 2023

The first thing to know is that HMRC take your return figures at face value. You are essentially assessing yourself and the figures are accepted upon submission. However, over the 12 months following submission, HMRC may enquire about your tax return. This could be a random check or there may be a particular element of the return HMRC want to question you on.


If you have underpaid tax, you will need to make a balancing payment to clear your tax bill by 31 January of the following the tax year. If you are required to make payments on account, the first payment will also be due on 31 January. As a reminder, "payments on account" are advance payments towards your tax bill (including Class 4 National Insurance if you're self-employed).

If your liability is under £3,000 and you are taxed via PAYE then you could repay your tax through an adjustment to your tax code. To add to that, if you prefer, you may be able to pay in regular monthly instalments. You can also get help if you cannot pay your tax bill on time. HMRC provides details on how to pay on their website under Pay your Self Assessment tax bill.


If you have overpaid tax, you will be due a refund from HMRC once your tax return has been submitted. Through the Taxd process, you have provided HMRC your bank details to collect your refund.

The general wait time is 10 working days once the return has arrived at the HMRC system. However, some repayments are subject to random security checks and may take longer. If you have any questions, the HMRC Self Assessment support team can help you.

HMRC also offer refunds through cheque or deductions from your next year's tax liability. This is not supported by Taxd.


HMRC use enquiries to check whether you are paying the right amount of tax. They use software to gather data from multiple sources to check specific returns. HMRC will also randomly select tax returns to audit. If this is the case for you, there is no need to worry.

HMRC should only ask for information that is reasonably required to check your tax position. Keep all your earnings and expenses documents to hand, either electronically or on paper, as you may need to share this with HMRC.

These enquiries are known as a Section 9A (s9A) and will be sent to your home address in writing. If you require additional support and guidance, at Taxd we can guide you through the process and liaise with HMRC on your behalf.


If you need to make a couple of changes to your return, HMRC will let you adjust your Self Assessment submission for 12 months after the statutory deadline. So, for the 2020/2021 tax year (due 31 January 2022) you may make any amendments by 31 January 2023. That’s true as long as you make sure your first submission was made by 31 Jan 2022.

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