Do Side Hustles Affect Tax Codes?
Reviewed by Ed WilkinsonLast updated: March 6, 2026 12:49 pm
Image credit: Yan Krukau @Pexels
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In today’s economy, many people take on a side hustle to supplement their income, from freelance writing and selling handmade goods online to driving for a ride-hailing service. These extra earnings can affect how and when you pay tax. Understanding how a side hustle interacts with your tax code and wider tax position helps you pay the right amount of tax and avoid unexpected bills.
Understanding Tax Codes
Your tax code, set by HM Revenue & Customs (HMRC), tells your employer or pension provider how much Income Tax to deduct under PAYE. It reflects your Personal Allowance1, benefits, and deductions for the tax year and is intended to collect the right amount of tax throughout the year. Tax codes apply to PAYE income (such as salaries or pensions), not directly to self-employment profits.
Components of Your Tax Code
A typical tax code consists of numbers and a letter. The numbers show your tax-free Personal Allowance divided by ten; the letter shows your circumstances. For example, an ‘L’ code in 2026/27 means you are entitled to the standard Personal Allowance. Codes such as BR, D0, D1, 0T or K may be used when your allowance is used elsewhere or to collect untaxed income.
Common Reasons for Tax Code Adjustments
Tax codes are not static and can be adjusted for a variety of reasons:
- Starting or stopping a job or pension, or having multiple employments.
- Government changes to allowances and thresholds. For 2026/27, the Personal Allowance remains £12,570 and is tapered once your income exceeds £100,000.
- Adjustments due to benefits in kind, such as company cars or health insurance, which are assessed for their cash equivalent and added to your taxable income.
- Other adjustments, such as under- or overpayments of tax from previous years, or estimated untaxed income you ask HMRC to collect via your code.
When you start a side hustle, whether your tax code changes depends on the nature of the income. If it is a second PAYE job or pension, HMRC may allocate your Personal Allowance to one job and apply a different code (for example, BR or 0T) to the other. If it is self-employment, your PAYE tax code will not usually change automatically; you normally report profits via Self Assessment and pay any tax due directly. You can ask HMRC to collect up to £3,000 of a Self Assessment bill through your tax code the following year.
Informing HMRC about Your Side Hustle
If your total trading income from self-employment is more than £1,000 in a tax year, you must register for Self Assessment2 by 5 October following the end of that tax year. You can use your Personal Tax Account to check and update your PAYE tax code and to tell HMRC about untaxed income if you want it coded out.
If your casual trading income is £1,000 or less (before expenses), the trading allowance may mean you do not need to register, unless you want to claim a loss or deduct actual expenses instead.
Keeping HMRC informed and ensuring your tax code is accurate helps maintain compliance and supports better financial planning. Being proactive can save you from potential stress and financial burden at the end of the tax year.
It’s always advisable to review your tax code after significant changes to your income or personal circumstances (for example, starting or stopping a job, receiving a benefit in kind, or asking HMRC to code out untaxed income). If you suspect your tax code is incorrect, contacting HMRC for clarification can prevent overpaying or underpaying tax.
Understanding and managing your tax code effectively can help you avoid unexpected liabilities, especially when you have multiple sources of income.
Impact of Side Hustles on Tax Codes
Side-hustle income is taxable and needs to be declared. The impact on your tax code depends on whether that income is taxed under PAYE (for example, a second employment) or through Self Assessment (self-employment).
When You Are Employed and Have a Side Hustle
If you are already employed and start a side hustle, tell HMRC which employment is your main job so your Personal Allowance is used in the right place. A second PAYE job will usually be assigned a code such as BR, D0, D1, or 0T, so the correct rate is deducted from that income. Your overall tax rate is based on total taxable income: in England, Wales and Northern Ireland in 2026/27, income above £50,270 is generally taxed at 40% (higher rate) and income above £125,140 at 45% (additional rate). Scotland has different bands and rates.
Changes in tax bands can affect your take-home pay. It can be helpful to use HMRC tools or reputable online calculators, or to seek professional advice, to understand how additional income might affect your tax liabilities.
Registering for Self-Assessment
If your gross trading income from the side hustle exceeds £1,000 in a tax year, you must register for Self Assessment. You then complete a tax return each year declaring all your income sources. Online returns are due by 31 January following the end of the tax year (paper by 31 October), and any tax due must also be paid by 31 January. If your tax bill is more than £1,000, you may need to make payments on account towards the next year. If you submit early and owe less than £3,000, you can usually ask HMRC to collect it through your PAYE tax code the following year.
Keep accurate records and claim only allowable expenses. If your side hustle involves working from home, you can normally claim a proportion of your home costs or use HMRC’s simplified flat-rate method. Self-employed people may also have National Insurance obligations; check HMRC guidance on Class 2 and Class 4 contributions, as rules and thresholds can change.
Implications of Not Reporting Side Hustle Income
Failure to report side-hustle income can lead to penalties for failing to notify, late filing and late payment, as well as interest on unpaid tax. It can also leave you on the wrong tax code, resulting in under- or overpayments that must be corrected later.
Paying the correct tax and National Insurance on self-employment profits can contribute to your National Insurance record, which affects your State Pension entitlement3. If your profits are low, check whether you need or wish to pay voluntary contributions.
In summary, being transparent with HMRC about your side hustle and understanding the resulting obligations are key to managing additional income efficiently and staying compliant.
Tax Responsibilities with Multiple Incomes
Having multiple sources of income requires careful management to ensure all tax obligations are met. Here are some key considerations:
- Keeping accurate records: Maintain detailed records of all your income and expenses. Keep digital copies where possible. Records for Self Assessment generally need to be kept for at least 5 years after the 31 January submission deadline for the relevant tax year, and you may need them if HMRC asks for evidence.
- Understanding expenses and allowances: Familiarise yourself with the types of expenses that can be deducted from taxable income. For example, if your side hustle involves using your home as an office, a proportion of utility bills and internet costs may be deductible, or you can use HMRC’s simplified flat rates. The rules can be nuanced, so consult HMRC guidance or a qualified tax professional.
- Staying informed about tax thresholds: Keep up-to-date with the latest tax bands and rates. In England, Wales and Northern Ireland for 2026/27, the Personal Allowance is £12,570 (tapered above £100,000), the higher rate threshold is £50,270, and the additional rate generally applies from £125,140. Scotland has different bands and rates. Understanding how your combined incomes sit against these thresholds helps you plan.
Additional Considerations for Multi-Income Tax Management
Aside from the fundamental practices, there are several other strategies to manage taxes with multiple income streams effectively:
- Use of technology for tracking: Leveraging financial software or apps can simplify tracking incomes and expenses, with helpful categorisation and reporting for tax preparation.
- Regular reviews of your financial status: Schedule monthly or quarterly reviews of your records so you can respond to changes and update in-year tax estimates where appropriate.
- Seeking professional advice: If your situation is complex or you are close to a higher band, a qualified accountant or tax adviser can help ensure you report correctly and claim appropriate reliefs.
- Budget for tax payments: Set aside money for your Self Assessment bill and, if applicable, payments on account due in January and July to avoid cash flow surprises.
By following these practices, you can manage your tax responsibilities more effectively, ensuring compliance and supporting your overall financial health.
Planning Ahead
Effective planning and understanding your tax position can help you manage your finances and avoid surprises at the end of the tax year. Consider using tools or software for tracking income and expenses, set reminders for key HMRC deadlines, and seek professional help if your affairs become complex.
A Financial Adviser Can Help
Managing the tax implications of multiple income streams can be challenging. A qualified accountant or tax adviser can help with Self Assessment and tax compliance. A financial adviser can help with broader planning across savings, investments and retirement, and, where relevant, how your tax position interacts with these areas.
With professional support, you can use allowances and reliefs appropriately while remaining compliant with tax laws. This content is educational and does not constitute personal tax advice.
FinancialAdvisers.co.uk specialises in connecting individuals with FCA-authorised and regulated financial advisers in their area. Whether you’re juggling multiple jobs, running a small business, or looking to improve your financial planning, they can help you find an adviser suited to your needs. This article is for general information only and does not constitute tax or financial advice.
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