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Managing Self-Assessment Tax Returns: A Step-by-Step Guide for Sole Traders

Welcome to our comprehensive guide on managing self-assessment tax returns for sole traders in the UK, brought to you by King and Taylor. We understand that navigating tax obligations can be complex, but you don’t have to do it alone.

At King and Taylor, we’re here to help you through every step of the process. If you have questions or need professional assistance with your self-assessment tax return, please reach out to us. Now, let’s dive into the essential steps for a stress-free tax season.

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Section 1: Understanding Self-Assessment Tax Returns

If you’re a sole trader in the UK, understanding and managing self-assessment tax returns is a fundamental aspect of your financial responsibilities. In this section, we’ll break down the key concepts and importance of self-assessment tax returns so you can navigate them with confidence.

What is a Self-Assessment Tax Return?

A self-assessment tax return is a document required by Her Majesty’s Revenue and Customs (HMRC) that you, as a sole trader, must complete each tax year. Its primary purpose is to report your total income, expenses, and other financial details to calculate the amount of tax you owe. Essentially, it’s a way for HMRC to ensure that you’re paying the correct amount of income tax and National Insurance contributions.

Why Do Sole Traders Need to Complete Self-Assessment Tax Returns?

  • Legal Requirement: First and foremost, completing a self-assessment tax return is a legal obligation in the UK. Failing to do so or submitting an inaccurate return can result in penalties and fines.
  • Accurate Tax Calculation: Self-assessment allows you to declare all your sources of income, including self-employment earnings, rental income, dividends, and any other taxable income. By doing so, you ensure that your tax liability is calculated accurately.
  • Claiming Deductions: Self-assessment also provides the opportunity to claim allowable expenses and deductions, which can reduce your taxable income and, consequently, your tax bill.

Key Deadlines

Understanding the deadlines for self-assessment tax returns is crucial to avoid penalties. In the UK, the tax year runs from April 6th to April 5th of the following year. Here are some key dates to keep in mind:

  • October 5th: This is the deadline for registering for self-assessment if you’re a new sole trader.
  • January 31st: This is the deadline for submitting your online tax return and paying any tax owed for the previous tax year. Missing this deadline results in penalties and interest charges.
  • July 31st: If you’re making a payment on account, this is the deadline for the first payment. The second payment is due on January 31st of the following year.

Penalties for Late or Inaccurate Submissions

Late or inaccurate submissions can lead to financial penalties. HMRC imposes penalties as follows:

  • Up to 3 Months Late: A penalty of £100, even if you don’t owe any tax.
  • 3-6 Months Late: Additional daily penalties of £10 per day, up to a maximum of £900.
  • 6-12 Months Late: A penalty of 5% of the tax owed or £300 (whichever is greater).
  • 12 Months Late or More: Another 5% penalty on the tax owed.

Section 2: Gathering Your Financial Documents

Before you dive into completing your self-assessment tax return, the first crucial step is to gather all the necessary financial documents. Having organized records makes the entire process smoother and ensures you don’t miss any income or expenses that could affect your tax liability. Here’s a checklist of the essential financial documents you’ll need:

  • Income Records: Start by collecting records of all your income sources, such as sales invoices, payments from clients or customers, and any income from other sources like dividends or investments. Ensure that these records are well-documented and clearly indicate the amounts received and the dates of transactions. A great way to keep track of records for your business is using software like Quickbooks or Xero, alternatively you can use an accountant like King and Taylor to keep track of things for you.
  • Expense Receipts: Keep receipts for all business-related expenses. This includes expenses like office supplies, equipment purchases, rent or mortgage payments for your business premises, utilities, and any costs associated with running your business.
  • Bank Statements: Your bank statements provide a clear overview of your financial transactions throughout the year. Download or gather all bank statements for your business accounts, as these will be invaluable for reconciling your income and expenses.
  • Mileage Records: If you use a vehicle for business purposes, keep a mileage log. This log should detail all journeys related to your business, including the date, destination, purpose of the trip, and the number of miles traveled.
  • Income from Other Sources: Don’t forget to account for any income from sources other than your primary business activities. This may include rental income, interest earned on savings or investments, or any freelance work you’ve taken on.
  • Pension Contributions: If you make contributions to a pension scheme, ensure you have records of these contributions. They may be eligible for tax relief.
  • Records of Assets: If you’ve purchased assets for your business, such as equipment or vehicles, keep records of these purchases, including the purchase price and date. You may be able to claim capital allowances on these assets.
  • Gift Aid Donations: If you’ve made charitable donations through Gift Aid, keep records of these donations as they can provide tax benefits.

By systematically gathering these financial documents and maintaining them throughout the year, you’ll not only make the self-assessment process more straightforward but also ensure that you maximize your deductions and accurately report your income. In the next sections, we’ll guide you through the process of registering for self-assessment and calculating your taxable income.

Section 3: Registering for Self-Assessment

If you’re new to self-assessment or becoming self-employed, one of your first steps is registering for self-assessment with HM Revenue and Customs (HMRC). This process is essential for establishing your tax identity and complying with UK tax regulations. Here’s a step-by-step guide on how to register:

1. Determine if You Need to Register:

  • New Sole Traders: If you’ve recently started working as a sole trader, you’ll need to register for self-assessment. Sole traders are individuals who run their own businesses and are personally responsible for their tax obligations. You can learn more about how to set up as a sole trader from the HMRC website here.
  • Other Circumstances: You may also need to register if you’ve earned income from other sources, such as rental income, dividends, or freelance work, and haven’t already been registered for self-assessment.

2. Collect Your Information:

Before you begin the registration process, gather the following information and documents:

  • Your National Insurance Number (NIN): This unique identifier is crucial for your tax records.
  • Personal Information: Your full name, address, contact details, and date of birth.
  • Business Details: If you’re registering as a sole trader, provide details about your business, including the start date and nature of your business activities.
  • Additional Income: Information about any additional sources of income you have, such as rental income or dividends.

3. Register Online:

The easiest way to register for self-assessment is online through the HMRC website. Follow these steps:

  • Visit the HMRC Self-Assessment registration page.
  • Select the option that best describes your situation, such as “I’m self-employed or I’m in a business partnership.”
  • Complete the online form with your personal and business information.
  • Verify your identity, which may involve answering security questions or providing identification documents.
  • Once your registration is complete, you’ll receive a Unique Taxpayer Reference (UTR) from HMRC. This is a 10-digit reference number unique to you and essential for all tax-related activities.

4. Keep Your UTR Safe:

Your UTR is like a key to your tax records, so it’s essential to keep it safe. You’ll need it when filing your self-assessment tax return, making payments, and communicating with HMRC. Store it securely and share it only with trusted professionals or organizations.

5. Register on Time:

Make sure to register for self-assessment promptly, ideally as soon as you become self-employed or earn income from other taxable sources. This will help you avoid any penalties for late registration.

By registering for self-assessment correctly and promptly, you’ll establish your tax identity and set yourself on the path to fulfilling your tax obligations accurately. In the next section, we’ll delve into calculating your taxable income, a crucial step in the self-assessment process.

Section 4: Calculating Your Taxable Income

Once you’ve registered for self-assessment and gathered your financial documents, the next step in managing your tax return as a sole trader is to calculate your taxable income accurately. This is a pivotal stage because it determines how much income tax and National Insurance contributions (NICs) you owe. Here’s how to go about it:

1. Understand Your Income Sources:

To calculate your taxable income, you must identify and aggregate all your income sources for the tax year. These sources may include:

  • Self-Employment Income: This is your primary source of income as a sole trader and includes earnings from your business activities.
  • Additional Income: Any other income sources, such as rental income, interest, dividends, or freelance work, must also be included.

You can learn more about what kind of income is taxable from this blog post by Litrg, What income is taxable?.

2. Deduct Allowable Expenses:

The good news for sole traders is that you can deduct allowable expenses from your total income. These are expenses that are directly related to your business activities and can be claimed to reduce your taxable income. Common allowable expenses include:

  • Office rent or workspace costs.
  • Utilities (e.g., electricity, internet, phone).
  • Office supplies and equipment.
  • Travel and mileage expenses for business-related journeys.
  • Marketing and advertising costs.
  • Insurance premiums.
  • Accountancy fees.
  • Bank charges and interest on business loans.

3. Calculate Your Taxable Profit:

To calculate your taxable income, subtract your allowable expenses from your total income. The result is your taxable profit, which is the amount on which you’ll pay income tax and NICs.

Taxable Income = Total Income – Allowable Expenses

Example: Calculate Your Taxable Profit for the Tax Year 2022/2023

Let’s assume you are a sole trader running a freelance web design business in the UK for the tax year 2022/2023. Throughout the year, you’ve kept detailed records of your income and expenses. Here’s a simplified breakdown of your financial situation:


  • Earnings from web design projects: £30,000
  • Interest earned from a business savings account: £500
  • Total Income: £30,500

Allowable Expenses:

  • Office rent: £5,000
  • Office supplies and equipment: £2,000
  • Website hosting and domain expenses: £1,000
  • Travel expenses for client meetings: £1,500
  • Marketing and advertising costs: £1,200
  • Total Allowable Expenses: £10,700


Now, let’s calculate your taxable profit step by step:

1. Total Income: £30,500

2. Total Allowable Expenses: £10,700

3. Calculate Taxable Profit:

Taxable Profit = Total Income – Total Allowable Expenses Taxable Profit = £30,500 – £10,700 Taxable Profit = £19,800

4. Apply Tax Bands and Rates:

For the tax year 2022/2023, the income tax rates in the UK are as follows:

  • Basic Rate (20%): Applies to income between £12,571 and £50,270.

Since your taxable profit (£19,800) falls within the basic rate band, you’ll pay income tax at the basic rate.

5. Calculate Income Tax:

Income Tax = Taxable Profit × Applicable Tax Rate Income Tax = £19,800 × 0.20 (basic rate) Income Tax = £3,960

6. National Insurance Contributions (NICs):

As a sole trader, you may also need to pay Class 2 and Class 4 NICs, depending on your income. Calculate your NICs separately based on the NICs rates and thresholds for the tax year.

7. Total Tax Liability:

Total Tax Liability = Income Tax + NICs

Let’s assume your NICs liability for the year is £1,000:

Total Tax Liability = £3,960 (Income Tax) + £1,000 (NICs) Total Tax Liability = £4,960

So, in this example, your taxable profit for the tax year 2022/2023 is £19,800, and your total tax liability, including Income Tax and NICs, is £4,960. You’ll need to make this payment to HMRC by the specified deadline to fulfill your tax obligations as a sole trader in the UK. Please note that this is a simplified example, and individual circumstances may vary, so it’s advisable to consult with a tax professional or use HMRC’s official resources for precise calculations and up-to-date tax rates.

4. Consider Capital Allowances:

If you’ve purchased assets for your business, you may be eligible for capital allowances. These allowances allow you to claim tax relief on the cost of these assets. The rules for capital allowances can be complex, so it’s advisable to seek professional advice to ensure you maximize your claims.

5. Account for Tax Bands and Rates:

In the UK, income tax is progressive, with different tax bands and rates based on your total taxable income. As of our last knowledge update in 2021, the income tax rates were as follows:

  • Basic Rate: 20% for income between £12,571 and £50,270.
  • Higher Rate: 40% for income between £50,271 and £150,000.
  • Additional Rate: 45% for income over £150,000.

Keep in mind that tax rates and thresholds can change, so it’s essential to check the current rates and bands with HMRC or a tax professional for the tax year you’re calculating.

6. National Insurance Contributions (NICs):

Don’t forget to account for NICs, which are separate from income tax. Sole traders typically pay Class 2 and Class 4 NICs. The rates and thresholds for NICs can also change, so ensure you’re using the correct figures.

By following these steps and accurately calculating your taxable income, you’ll have a clear understanding of your tax liability. In the next section, we’ll guide you through the process of completing the self-assessment tax return form, where you’ll report your income, expenses, and deductions to HMRC.

Section 5: Completing the Self-Assessment Form

Completing the self-assessment tax return form is a critical step in the tax filing process for sole traders in the UK. This is where you provide HM Revenue and Customs (HMRC) with all the necessary details about your income, expenses, and other financial matters. Here’s a step-by-step guide to help you navigate this important stage:

1. Access the Self-Assessment Form:

You can complete your self-assessment tax return online using the HMRC website. Log in to your online account or register for one if you haven’t already.

2. Start a New Tax Return:

Begin by selecting the option to start a new tax return for the relevant tax year. Ensure that you’re completing the correct tax return for the specific tax year.

3. Personal Details:

Provide your personal information, including your name, address, National Insurance Number (NIN), and Unique Taxpayer Reference (UTR). Verify that all details are accurate and up to date.

4. Income:

Report all sources of income, including your self-employment income and any other income streams (e.g., rental income, dividends, freelance work).

Ensure that you enter the correct amounts for each source of income, and double-check that your records match the figures you provide.

5. Allowable Expenses:

Deduct allowable expenses from your total income. You’ll need to list these expenses on the form, specifying the nature and amount of each expense.

Be thorough and accurate when reporting expenses. Keep receipts and records to support your claims in case of an audit.

6. Capital Allowances:

If you’re eligible for capital allowances due to assets you’ve purchased for your business, declare these on the form. Ensure you’re using the correct rates and figures.

7. Tax Bands and Rates:

Be aware of the tax bands and rates applicable to your total taxable income. As a sole trader, you’ll need to calculate the income tax you owe based on these rates.

8. National Insurance Contributions (NICs):

Include your Class 2 and Class 4 NICs on the form, ensuring that you accurately report your NICs liability.

9. Additional Information:

The self-assessment form may have sections where you can provide additional information or explanations for specific circumstances. Use these sections to clarify any exceptional financial matters.

10. Review and Check for Errors:

Before submitting the form, carefully review all the information you’ve entered. Check for errors, omissions, or inconsistencies that could trigger queries from HMRC.

11. Submit the Form:

Once you’re confident that your self-assessment tax return is accurate and complete, submit it electronically through the HMRC online portal.

12. Payment:

If you owe tax, ensure that you make the payment by the deadline. HMRC provides various payment options, including online banking, direct debit, and credit card payments.

13. Keep Records:

Retain copies of your completed tax return, supporting documents, and payment receipts for at least six years. HMRC may request these documents for verification or audit purposes.

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Section 6: Submitting Your Tax Return

Once you’ve completed your self-assessment tax return, the next crucial step is to submit it to HM Revenue and Customs (HMRC). This section provides a step-by-step guide on how to submit your tax return, whether you’re filing online or using the paper form:

Submitting Your Tax Return Online:

Filing your tax return online is the most common and convenient method. Here’s how to do it:

1. Log in to Your HMRC Online Account:

  • Visit the HMRC website and log in to your online account using your credentials. If you don’t have an online account, you can register for one on the website.

2. Select “Complete a Tax Return”:

  • Once logged in, select the option to “Complete a Tax Return” from your account dashboard.

3. Complete the Online Form:

  • Follow the on-screen instructions to complete the tax return form. Enter your income, expenses, allowances, and other relevant information as discussed in Section 5.

4. Review and Confirm:

  • Before submission, carefully review the entire form to ensure accuracy. Double-check your figures and calculations to avoid errors.

5. Submit Electronically:

  • After confirming that all information is accurate, submit your tax return electronically through the HMRC portal. You will typically receive a confirmation message or reference number upon successful submission.

6. Payment (if Applicable):

  • If you owe income tax or National Insurance contributions (NICs), make the payment as outlined in Section 5. HMRC offers various payment methods, including online banking, direct debit, and credit card payments.


It’s essential to adhere to the filing deadlines set by HMRC. As of our last knowledge update in 2021, the deadline for online submissions and payments is typically January 31st following the end of the tax year. For paper returns, the deadline is usually earlier, around October 31st. However, these deadlines may change, so always verify the current deadlines for the tax year in question.

Section 7: Paying Your Tax Bill

Once you’ve completed and submitted your self-assessment tax return, it’s time to ensure that you pay the amount owed to HM Revenue and Customs (HMRC) promptly and accurately. Here’s a guide on how to make your tax payment:

1. Calculate Your Tax Liability:

  • Before making your payment, ensure that you have an accurate calculation of your tax liability based on the information provided in your self-assessment tax return. This includes both income tax and National Insurance contributions (NICs).

2. Payment Methods:

  • HMRC offers several payment methods to make it convenient for taxpayers. These include:
    a. Online Banking: You can use your bank’s online services to make a payment directly to HMRC. Ensure that you use the correct payment details, which can be found on the HMRC website.
    b. Direct Debit: Set up a direct debit payment plan with HMRC. This is a convenient option that allows you to spread your tax payments throughout the year.
    c. Debit or Credit Card: You can pay your tax bill using a debit or credit card through the HMRC website. Be aware that there may be associated processing fees for credit card payments.
    d. Bank Transfer: Make a payment via bank transfer using the bank details provided by HMRC. Ensure that you include the correct reference number to identify your payment.
    e. Cheque: If you choose to pay by cheque, make it payable to “HM Revenue and Customs” followed by your Unique Taxpayer Reference (UTR). Be sure to send it with sufficient time to meet the payment deadline, as cheque processing can take longer.

3. Payment Deadlines:

  • To avoid penalties and interest charges, it’s crucial to make your tax payment by the specified deadline. The deadline for tax payments is typically the same as the deadline for submitting your self-assessment tax return, which is January 31st following the end of the tax year. However, verify the exact deadline for the tax year in question, as it can change.

4. Payments on Account:

  • If your tax bill is above a certain threshold, you may be required to make payments on account. These are advance payments toward your next year’s tax bill. Payments on account are typically due in two equal installments, one by January 31st and the other by July 31st.

5. Record Keeping:

  • After making your tax payment, keep a record of the payment confirmation or receipt. This documentation is essential for your records and may be required for future reference or audits.

6. Seek Professional Advice:

  • If you’re uncertain about your tax bill or need assistance with payment arrangements, consider consulting with a tax professional or contacting HMRC directly. It’s better to seek guidance and ensure compliance with tax regulations. King and Taylor can help with any professional advice so please get in touch.

Remember that timely and accurate tax payments are essential to avoid penalties and ensure that you remain compliant with your tax obligations as a sole trader. If you have any questions or require further assistance with your tax bill, don’t hesitate to reach out to King and Taylor for expert advice and support.

Section 8: Record Keeping and Future Tax Planning

Effective record-keeping and future tax planning are key to maintaining financial stability as a sole trader. They help you stay organized, reduce the stress of tax season, and ensure you’re prepared for the road ahead. Here’s how to manage these essential aspects of your financial responsibilities:


1. Organized Record Keeping:

  • Keep thorough and organized records of your financial transactions throughout the year. This includes income, expenses, bank statements, receipts, invoices, and any other financial documentation.
  • Consider using accounting software or apps designed for sole traders to streamline record keeping. These tools can help automate data entry and categorize expenses, making it easier to track your financial activities.
  • Set up a filing system to store physical copies of receipts and important documents. Label files by category, such as income, expenses, and taxes.

2. Regular Reconciliation:

  • Reconcile your financial records with your bank statements and other financial documents on a regular basis. This helps identify any discrepancies or errors early on.
  • Ensure that all income and expenses are accurately recorded. Reconcile your accounts monthly or quarterly to catch and correct any errors promptly.

3. Tax Planning:

  • Engage in proactive tax planning to minimize your tax liability legally. This includes:
    a. Understanding Allowable Deductions: Stay informed about the allowable expenses and deductions relevant to your business. Keep records of all deductible expenses to reduce your taxable income.
    b. Tax-Efficient Business Structure: Consider whether your current business structure is the most tax-efficient option for your circumstances. Sole traders, for example, may benefit from exploring alternative structures like limited companies.
    c. Advance Tax Payments: If you anticipate that your tax bill will be significant, consider making advance tax payments throughout the year to avoid a large lump-sum payment at the end of the tax year.
    d. Utilizing Tax Credits: Explore tax credits and incentives that may apply to your business. For example, research Research and Development (R&D) tax credits or Small Business Rate Relief.

4. Consult a Tax Professional:

  • If you’re unsure about the best tax planning strategies for your business or have complex financial arrangements, consider seeking guidance from a tax professional or accountant. They can provide personalized advice tailored to your specific situation.

5. Long-Term Financial Goals:

  • Consider your long-term financial goals and how your tax planning aligns with them. Whether you’re saving for retirement, expanding your business, or investing in assets, effective tax planning can help you achieve these objectives efficiently.

6. Stay Informed:

  • Tax laws and regulations can change from year to year. Stay informed about any changes that may affect your tax obligations or opportunities for tax savings.

7. Periodic Reviews:

  • Periodically review your financial records and tax strategies to ensure they are in line with your current business activities and financial goals. Adjust your approach as needed.

Effective record keeping and proactive tax planning can help you not only meet your current tax obligations but also pave the way for a financially stable future as a sole trader. By staying organized and informed, you can maximize your deductions, minimize your tax liability, and make sound financial decisions for your business. If you need professional assistance with record keeping or tax planning, don’t hesitate to reach out to King and Taylor for expert guidance and support.

Conclusion: Self-Assessment

Navigating self-assessment tax returns as a sole trader in the UK can be complex. This guide has broken down the essential steps, from understanding the process to making your tax payment.

At King and Taylor, accountants in Gravesend, Kent, we’re here to simplify your tax responsibilities. If you have questions or need professional assistance, reach out to us. We’re dedicated to supporting your financial success, ensuring compliance, and helping you plan for the future. Get in touch today to ease your tax journey and gain financial peace of mind.