How to File a Self-Assessment Tax Return Online – A step-by-step guide

Are you filled with trepidation at the prospect of completing your self-assessment tax return online? For many, the process of filing tax returns can be a daunting task, but with proper preparation and a clear understanding of the process, it can become a more manageable endeavor. In this article, we will provide you with a step-by-step guide on how to complete your self-assessment tax return online. We will also cover key dates, allowable expenses, charity donations, penalties for late filing, payment options, and the advantages of using a tax return accountant.

Do You Need to File a Tax Return?

For most employees and pensioners in the UK, income tax is automatically deducted from wages and pensions. However, if you have income from sources not subject to tax deduction and that exceeds a certain level, you’ll need to report it in a self-assessment tax return. 

Here are some common scenarios where you’ll need to file a self-assessment tax return: 

  • Self-Employment: If you were self-employed as a sole trader in the previous tax year and earned more than £1,000, you must file a tax return. 
  • Business Partnership or Director: If you were a partner in a partnership or a director of a limited company, and your income wasn’t taxed at source, you’ll need to file a tax return. 
  • Specific Sectors: Even if your primary income is from wages or pensions, you may still need to file a return if you work in specific sectors, earn over £100,000 through a PAYE salary scheme, or have other untaxed income sources like renting, tips and commission, savings, investments, dividends, or foreign income. 
  • Claiming Income Tax Relief: You can also file a tax return to claim income tax relief or prove self-employment status, for instance, to claim Tax-Free Childcare or maternity allowance. 

Key Dates and Deadlines

The details of UK tax year dates are: 

  • For self-employment and sole traders, the deadline to register for self-assessment is October 5th for the tax year 2022/23. 
  • The deadline for filing paper tax returns is October 31, 2023, while the online deadline is January 31, 2024. 
  • Two payments on account may be due after your first tax return. The first is due by January 31, and the second by July 31. 

How to Register and File a Tax Return Online?

HMRC Online Account: If you’ve never filed a HMRC tax return online before, you must register for an HMRC online account. After registering, HMRC will send you an activation code, so plan for the time it takes to receive this code.

Gather Required Information: Before you start your online tax return, gather the necessary information. This includes your Unique Taxpayer Reference (UTR), National Insurance number, employer reference (if applicable), and documents like P60, P11D, P45, pay slips, and P2 PAYE coding notice etc.

Completing the Tax Return: The online tax return form will ask for personal details, sources of income or gains, income from bank or building society interest, pensions, share dividends, and other financial information. Ensure you document everything, keep copies of receipts, and carefully enter figures.

Document and Verify: Keep records of all the information used in your self-assessment for up to five years after the January 31 HMRC self-assessment registration deadline. This is essential to avoid potential penalties in case of an HMRC review.

Allowable Expenses

If you are self-employed, your business incurs various expenses that can be deducted from your income to calculate taxable profits. Allowable expenses can include office costs, uniforms, staff costs, financial costs, professional fees (like accountants or lawyers), business premises expenses, and advertising or marketing expenses. Sole traders can claim simplified expenses or use the trading allowance to reduce their tax bill.

Charity Donations on Tax Returns

Donations to charities or community amateur sports clubs can attract tax relief. Include all charitable donations in your tax return. The tax relief can benefit either you or the charity, depending on how the donation is made. Make sure to keep records of your donations for tax purposes.

Penalties for Filing Late and Appeals

Late filing or late payment can lead to penalties. You can appeal against a penalty if you have a reasonable excuse. The penalties vary based on the delay, and interest may be charged on late payments. Filing late increases the chance of HMRC scrutinizing your return, so complete it early to avoid stress and missed deadlines.

How to Pay Your Tax

After completing your self-assessment return online on government gateway for self-assessment, HMRC will notify you of the tax amount owed. You’ll need to pay tax by 31 January and may also need to make two payments on account for the upcoming tax year. The first payment is due on January 31, and the second on July 31. Various payment methods include online or telephone banking, CHAPS, debit or corporate credit card, BACS, direct debit, or by cheque through the post. Payment at the Post Office is no longer an option.

Reasons to Consider Using a Tax Return Accountant

Many individuals and business owners prefer using an accountant to complete their self-assessment tax returns. While it may involve additional costs, here’s why it can be worthwhile: 

  • Expertise: Accountants like Interface Accountants are knowledgeable about income tax rules, ensuring you claim all allowable expenses and allowances correctly. 
  • Avoiding Errors: Accountants help minimize the risk of mistakes in your tax return, which otherwise can lead to penalties. 
  • Dispute Handling: They can assist in managing disputes with HMRC if issues arise. 
  • Ongoing Support: Self Assessment Accountants often provide year-round support, ensuring your business remains compliant and helping with real-time performance tracking, especially when using cloud accounting software. 

While many self-employed individuals choose to do their first self-assessment on their own to gain a better understanding of the process, hiring an accountant becomes an attractive option as the business grows and tax rules become more complex. 


Filing your self-assessment tax return online can seem intimidating, but with the right preparation and information at your disposal, it can be a manageable task. Planning is key, and a stress-free experience comes with early completion and accurate record-keeping. Whether you choose to file your tax return yourself or opt for an accountant’s assistance, the most crucial aspect is ensuring you meet HMRC’s deadlines and maintain accurate financial records. 

If you decide to engage accountants in Slough, accountants in Watford, accountants in London, or accountants in Ealing, it’s essential to shop around to find a reputable and cost-effective professional. Remember that the cost of using an accountant can often be offset by tax savings, avoiding mistakes, and receiving professional advice that helps your business succeed. 

By following these steps, you’ll navigate the self-assessment process more comfortably and ensure compliance with HMRC regulations. Don’t hesitate to reach out to HMRC for guidance if you have questions to prevent any potential penalties due to inaccuracies in your self-assessment.