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How Do I Complete and Submit an SA100 Tax Return?

SA100 Tax Return

Navigating the tax system’s complexities can be quite intimidating. Initially, you must determine your responsibilities, actions, and timelines, which marks the beginning. Moreover, it feels like learning a foreign language, especially when deciphering the various names and phrases in the UK system.

Furthermore, if you are not an employee, you must strive to grasp the tax system’s basics; otherwise, you risk facing harsh penalties and charges.

Consider the SA100 tax form and self-assessment. While you might know about the need for a self-assessment, the integral role of the SA100 form in this process might be new to you. Most people recognize the term ‘self-assessment’ without understanding its components.

However, understanding the SA100 and its significance is crucial. The self-assessment process involves filling out the SA100 form to complete your assessment.

What is an SA100?

tax form

An 8-page tax form is necessary for eligible individuals to complete their self-assessment. Specifically, it evaluates all income types, including interest, dividends, pensions, annuities, and state benefits. Additionally, it allows the inclusion of tax-offsetting information for gift aid and charitable donations. Furthermore, it addresses over/underpayment issues by enabling tax refund or underpayment reporting.

Importantly, the SA100 form is vital for HMRC to determine your tax obligations, although it might not be the only required document. In some cases, your situation may necessitate additional forms for income like capital gains, UK property, or foreign gains.

To ensure compliance, understanding how to access, complete, and submit the SA100 to HMRC is crucial. Let’s delve into the SA100 form with a step-by-step breakdown.

Who must complete an SA100?


Contrary to common belief, not only self-employed individuals need to complete a self-assessment; anyone with untaxed income must fill out an SA100. This includes:

  • Self-employed individuals
  • Company directors with non-PAYE income
  • Employees earning untaxed tips and commissions
  • Landlords and let owners
  • UK residents with overseas income
  • Individuals realizing taxable asset gains
  • Side business operators
  • High earners with income over £100,000

Most UK income types outside the standard PAYE system require completing an SA100 form, aiding HMRC in tax calculation.

The SA100 Form Explained

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Filling out the SA100 online via the self-assessment website or requesting a paper form from HMRC is possible.

The form assesses potential income sources from self-employment or business, with supplementary forms available for uncovered income types.

Sections of the SA100 include:

information tab
  • Personal details
  • Supplementary income question page
  • Income assessment fields
  • Tax reliefs
  • Student loans and state benefits
  • Tax over/underpayment fields
  • Additional information section

A step-by-step guide helps simplify the SA100 completion process.

Completing the SA100: Step-by-Step

completed steps
  • Gather all necessary documents for income reporting.
  • Choose between online or paper completion.
  • Review the ‘What makes up your tax return’ page and select relevant supplementary forms.
  • Fill in the ‘Income’ page, excluding ISAS or save-as-you-earn schemes.
  • Report UK pensions, annuities, and other state benefits.
  • Complete the tax reliefs page, excluding employer pension scheme contributions.
  • Note down student loan repayments or high-income child benefit charges if applicable.
  • Address personal circumstances in the final sections, including marriage allowance or incorrect coronavirus support claims.
  • Provide tax underpayment or overpayment details and banking information for refunds.
  • Include tax advisor information and sign the form, indicating any supplementary pages or provisional figures used.

Submission Deadlines

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  • Paper returns are due by the end of October (31st October 2023 for the 23/24 tax year).
  • Digital returns have a later deadline, by the end of January (31st January 2024 for the 23/24 tax year).
  • For automatic tax collection from wages and pensions, submit by the 30th of December.

If you’re seeking assistance with completing and submitting your SA100 Tax Return, don’t hesitate to let our team at Count know. We’re here to provide the help and guidance you need to make the process seamless and stress-free. Reach out to us today!

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