What is an SA100 form?

What is an SA100 form?
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    Disclaimer: This article is based on legislation which was correct at time of publishing on March 6, 2023

    The SA100 form is the internal reference number for the form, more commonly known as the self-assessment tax return. This may be required for a number of reasons, and once HMRC has issued a return for completion, it is important that the return is submitted.

    Completing your SA100 form can be overwhelming, but at Butt Miller, we’re here to help. Our team can assist you in filling out your self-assessment tax return and even guide you on how to claim tax reliefs. So let us take the stress out of your SA100 form by looking at our informative guide.

    Who needs to complete an SA100 form?

    UK taxpayers are not automatically required to complete the SA100 form.

    HMRC will issue a return to anyone they believe has untaxed income or may need to pay more tax under PAYE, such as the self-employed or those receiving income from renting property.

    Once issued with a return, the taxpayer must complete and submit it to HMRC by the due date advised by HMRC.

    Taxpayers who have yet to be issued a return but have a tax liability arising from income not taxed under PAYE should register for self-assessment. Notification of liability should be made to HMRC by 5 October following the tax year in which the liability arises.

    HMRC’s guidance implies that tax return forms are required under other circumstances. Still, some notable appeals have shown that their guidance does not necessarily reflect the legislation on when a return is required.

    For many years HMRC guidance had stated that a company director was automatically required to submit a tax return, but this has changed following a successful challenge through the courts. Company directors only need to fill in returns if they have non-PAYE sources of income that produce a tax liability.

    Non-UK residents should bear in mind that they may need to fill in a self-assessment tax return to disclose income arising in the UK, such as UK property income.

    An individual who does not otherwise need to fill in an SA100 tax return may choose to register to submit online tax returns if they are due a significant tax rebate for a tax year. This can arise when you need to claim expenses against earnings, or you make large pension contributions.

    The advantage of submitting an online return is that HM Revenue and Customs tend to issue refunds claimed online much more quickly than refunds claimed in other ways.

    How do I obtain an SA100 form?

    If you are not automatically issued a form by HM revenue and customs, you will need to request a self-assessment reference number if you have yet to be given one.

    Most UK taxpayers can request an SA100 form online which will be issued with their reference number within a couple of weeks.

    Once you have the reference number, you can register for an online account through the government gateway, enabling you to complete the return online.

    How do you complete an SA100?

    The SA100 form is the primary tax return, comprising 8 pages, which requires the personal details of the taxpayer and includes sections for the more common sources of income.

    The form requires little detail and mostly requires summarising income and outgoings. Interest received from multiple bank accounts is just reported as a single figure, being the total of the interest received. It is not necessary to provide any more detail. Expenses relating to self-employment or rental profits are split into categories, and again it is not essential to provide more detail with the return.

    Certain sections will require additional detail to be reported, and the return includes spaces for these extra details (known as white space). The guidance notes advise when further detail is needed.

    The Capital Gains pages require additional details, which may be added to the white space or as a separate attachment to the return.

    HMRC has been encouraging taxpayers to submit their returns online, and these can be completed through the HMRC website. However, several commercial products are available to help with filing your tax return online.

    When filing additional pages online, these will be added as pdf files.

    What are the main sections of the self-assessment tax return?

    The self-assessment return will comprise the main SA100 form, which includes pages for common investment income sources such as interest and dividends and sections for claiming tax reliefs that are regularly claimed.

    Supplementary pages disclose income from such sources as self-employment profits, rental income, employment income, foreign income and report profits realised from disposing of assets (Capital Gains).

    The most common type of income reported through a tax return will profit from self-employment or income from renting out property.

    Occasionally there will be additional forms not covered by the supplementary forms or which are required to be submitted to HMRC. You can submit additional forms as an attachment to the return itself.

    The tax return form will mostly run to less than 20 pages but can be significantly more for anyone with a complex tax situation.

    When does it need to be submitted?

    The due date for submitting a tax return online is 31 January, following the end of the tax year, or 3 months after the return is issued, if that is later. However, if you submit the return on paper, in most cases, the deadline for submitting a paper tax return is 31 October, following the end of the tax year.

    Get help with your self-assessment tax return from Butt Miller

    If you think you may need to fill in a self-assessment tax return, talk to a tax adviser first about your tax situation. At Butt Miller, we have experience completing the returns that need to be submitted to HMRC and managing complex scenarios.

    Want to learn more about self-assessment tax returns? Check out our guide here.

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