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How to file a self assessment tax return


Filing a self-assessment tax return might seem like a daunting task, but it doesn’t have to be. Whether you’re a self-employed individual, a freelancer, a business owner, or even just someone with multiple income sources, understanding how to file your self-assessment tax return is crucial to ensure you meet your tax obligations accurately and on time. In this comprehensive guide, we will walk you through the process, step by step, so you can file your self-assessment tax return with confidence.

Register for Self-Assessment

Before you can file your self-assessment tax return, you need to register with Her Majesty’s Revenue and Customs (HMRC). You must do this by October 5th following the end of the tax year in which you need to file a return. The tax year in the UK runs from April 6th to April 5th of the following year. For example, if you need to file a return for the tax year ending on April 5th, 2023, you must register by October 5th, 2023.

You can register online on the HMRC website or by completing and mailing form SA1 to HMRC. Once you’ve registered, HMRC will provide you with a Unique Taxpayer Reference (UTR) and set up your online account for self-assessment.


Gather Your Documents

Before you start filling out your self-assessment tax return, gather all the necessary documents and information. This includes:

Personal details: Your National Insurance number, Unique Taxpayer Reference (UTR), and any relevant correspondence from HM Revenue and Customs (HMRC).


Income details: Records of all your income sources, including payslips, invoices, bank statements, and P60s or P45s from employers (if applicable).



Keep track of any allowable expenses related to your income sources. These may include office supplies, travel expenses, and professional fees.

Tax reliefs and allowances: Be aware of any tax reliefs or allowances you are eligible for, such as the Marriage Allowance or Blind Person’s Allowance.

Register with HMRC

If you haven’t already registered for self-assessment with HMRC, you’ll need to do so. Visit the HMRC website and complete the registration process. You’ll receive a Unique Taxpayer Reference (UTR) if you don’t already have one.

Choose the Right Tax Year

Self-assessment tax returns cover a specific tax year in the UK, which runs from April 6th to April 5th of the following year. Make sure you select the correct tax year for your return.

Use the Right Tax Software or Paper Forms

Most people these days prefer to file their self-assessment tax returns online. HMRC provides a user-friendly online platform for this purpose. To use it, you’ll need to create an online account and log in to the “Self Assessment” section. Alternatively, you can download and fill out a paper tax return form from the HMRC website.



Complete the Self-Assessment Tax Return

The self-assessment tax return consists of various sections, each of which requires specific information. Here’s an overview of what you’ll need to complete:

Personal Information: Fill in your name, address, National Insurance number, and UTR.

Income: Report all your income sources, including employment income, self-employment income, rental income, and any other sources of income. You’ll need to provide figures for each source and total them up.

Expenses: Deduct allowable expenses from your income to calculate your taxable profit. Be sure to keep detailed records of all your expenses.

Tax Reliefs and Allowances: 

Declare any tax reliefs or allowances you are eligible for. These may include Marriage Allowance, Blind Person’s Allowance, or tax deductions for pension contributions.

Taxable Income: Calculate your taxable income by subtracting allowable expenses and tax reliefs from your total income.

Tax Owed: Use the tax rate applicable to your income to calculate the amount of tax you owe. Be aware of different tax rates for various income thresholds.

Payments and Overpayments: If you have any tax overpayments from previous years or payments on account, make the necessary adjustments.

Payment: Calculate the total amount you owe to HMRC. You can pay your tax bill online, by bank transfer, or by cheque.


Filing your self-assessment tax return on time is crucial to avoid penalties. The deadline for filing your self-assessment tax return online is typically January 31st following the end of the tax year. However, it’s a good idea to start the process well in advance to ensure you have enough time to gather all the required information and complete the return accurately.

Submit Your Tax Return

Once you have filled out all the necessary sections and reviewed your self-assessment tax return for accuracy, submit it online through the HMRC website or send the paper form to the address provided on the form. Keep a copy of your tax return and any supporting documents for your records.


If you owe tax, make sure to pay it by the deadline. Late payments can result in interest charges and penalties. HMRC provides various payment methods, including online payments, bank transfers, and cheque payments.

Tax Calculations and Refunds

After submitting your tax return, HMRC will calculate your final tax liability. If you’ve overpaid taxes during the year, you’ll receive a refund. On the other hand, if you underpaid, you’ll need to settle the outstanding amount.

Keep Records

It’s essential to maintain accurate records of your income, expenses, and tax-related documents. HMRC may request supporting evidence or audit your tax return, and having well-organized records will make this process much smoother.



Filing a self-assessment tax return is a fundamental responsibility for many individuals and businesses in the UK. While it may seem daunting at first, following the steps outlined in this guide can help simplify the process and ensure you meet your tax obligations accurately and on time. Remember to stay organized, gather all necessary documents, and seek professional advice if you have complex tax situations. By staying on top of your tax responsibilities, you can avoid penalties and ensure your finances are in good order.

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