Starting a side business alongside your job in the UK

Checking your employment contract

Before you print business cards for your gardening service or take bookings for a weekend bakery, you must review your current employment contract. Many UK employers include clauses regarding outside interests or secondary employment. Some contracts outright forbid working for another entity, while others simply require you to seek written permission first.

Conflict of interest is a significant factor. If you are a graphic designer by day, your employer may object to you taking private design clients in the evening. However, they might be perfectly happy for you to run a pottery stall or teach yoga. It is usually better to have a transparent conversation with your manager or HR department than to risk a breach of contract that could lead to disciplinary action.

Registering with HMRC

When you start earning money outside of your PAYE job, you transition into being a sole trader in the eyes of the government. You do not necessarily need to register the moment you sell one loaf of bread, as there is a specific allowance for small amounts of casual income. You should check the current 'Trading Allowance' figure on the GOV.UK website to see if your annual side income exceeds this limit.

Once your turnover goes above that allowance, you must register for Self Assessment with HMRC. This does not mean you are quitting your job; it simply means you will tell the tax office about all your income sources so they can calculate the correct tax. You will be responsible for filing a tax return annually. It is worth setting aside a portion of every payment you receive into a separate savings account so you are not caught short when the tax bill arrives.

Managing your tax and National Insurance

Your employer will continue to deduct tax and Class 1 National Insurance from your salary through the PAYE system. Your side business income will be taxed at your marginal rate. For example, if your day job already pushes you into the higher rate tax bracket, every pound you earn from your freelance coaching or craft business will also be taxed at that higher rate.

Self-employed individuals also pay different classes of National Insurance. The rules and thresholds for these payments change frequently, so you should consult the latest guidance on the HMRC website regarding Class 2 and Class 4 contributions. Keeping detailed records of your business expenses—such as ingredients for a baker or clay for a ceramicist—is vital, as these costs can be deducted from your turnover to work out your taxable profit.

Working hours and the 48-hour limit

In the UK, the Working Time Regulations generally limit the average working week to 48 hours. While many people choose to 'opt out' of this limit by signing a voluntary agreement with their employer, you should be aware of how your side business impacts your total hours. Overworking can lead to burnout, which might affect your performance in your main job and the quality of your own business.

Practical time management is essential for a sole trader with a day job. You might consider the following steps to stay organised:

• Dedicate specific evenings or weekend blocks to your business rather than multitasking.
• Use an online booking system to handle appointments so you aren't answering messages during your employer's time.
• Set clear expectations with your clients regarding your response times.
• Automate your invoicing to reduce the time spent on administration.
• Review your energy levels monthly to ensure your schedule is sustainable.

Professional indemnity and insurance

Depending on your trade, you may need specific insurance. A hairdresser working from home or a tattoo artist needs public liability insurance to protect against claims of injury or property damage. Professional indemnity insurance is common for consultants or coaches who give advice.

Your employer's insurance will not cover your private business activities. Even if you are working from a home studio, you should notify your home insurance provider. Some standard domestic policies are invalidated if you run a business from the property, especially if you have clients visiting you or if you store expensive commercial equipment and stock on-site.

Impact on student loans and benefits

If you are repaying a student loan through your salary, HMRC will also calculate student loan repayments on your self-employed profits once you file your Self Assessment. This can sometimes result in a larger-than-expected year-end payment. Similarly, if you receive any state benefits or tax credits, additional income from a side business must be reported to the Department for Work and Pensions (DWP) or HMRC, as it may affect your eligibility or the amount you receive.

This article provides general information and does not constitute legal, financial, or tax advice. Rules regarding taxation, employment law, and thresholds change regularly. Always check the official GOV.UK website or consult a qualified accountant or legal professional for the most current guidance specific to your situation.