Freelancing Alongside a Full-Time Job — Tax Guide

The Accounted Business Team·3 March 2026·10 min read

Freelancing alongside a full-time job has become incredibly common. Maybe you are a graphic designer picking up evening projects, a copywriter taking on weekend commissions, a developer building apps on the side, or a consultant using your industry expertise to advise smaller businesses. Whatever the skill, there has never been more opportunity to monetise it outside your nine-to-five.

But juggling two income sources means juggling two sets of tax obligations. Your employer handles your PAYE, but your freelance earnings? Those are entirely your responsibility. Let us break down exactly how it all works.

Do You Need to Register as Self-Employed?

If your freelance income exceeds the £1,000 trading allowance in a tax year, you need to register as self-employed with HMRC. This is on top of your existing employment — the two exist side by side.

The £1,000 threshold is based on your gross freelance income (total invoiced amount), not your profit after expenses. So if you invoiced £1,200 but spent £800 on software and travel, leaving you with just £400 profit, you still need to register because your gross income exceeded £1,000.

If your freelance income is £1,000 or less, the trading allowance covers it — no registration, no return, no tax. But for most people freelancing regularly alongside a job, £1,000 comes and goes pretty quickly.

Registration is straightforward and can be done online through the Government Gateway. For a complete walkthrough, see our guide on how to register as self-employed with HMRC.

How Your Tax Is Calculated

This is the part that causes the most confusion, so let us take it step by step.

Your employment income

Your employer deducts income tax and National Insurance from your salary through PAYE (Pay As You Earn). Your personal allowance of £12,570 is usually applied through your tax code (typically 1257L), meaning your first £12,570 of salary is tax-free.

Your freelance income

Your freelance profit (income minus allowable expenses) is added to your employment income to determine your total taxable income for the year. The combined total is then taxed according to the standard income tax bands for 2025/26:

Personal Allowance: £12,570 (0%)
Basic rate: £12,571 – £50,270 (20%)
Higher rate: £50,271 – £125,140 (40%)
Additional rate: Over £125,140 (45%)

Example

Let us say you earn £35,000 from your full-time job and £8,000 in freelance profit.

Your total income is £43,000. Your personal allowance (£12,570) is already accounted for through PAYE, so your freelance profit of £8,000 is taxed entirely at the basic rate of 20%.

Income tax on freelance earnings: £8,000 × 20% = £1,600

Now imagine you earn £48,000 from your job and £6,000 from freelancing. Your total income is £54,000, which crosses into the higher rate band.

£2,270 of your freelance income falls within the basic rate band (£48,000 + £2,270 = £50,270)
£3,730 falls into the higher rate band

Income tax on freelance earnings: (£2,270 × 20%) + (£3,730 × 40%) = £454 + £1,492 = £1,946

That higher rate tax can be a bit of a shock if you are not expecting it. This is why it is so important to know your combined income and plan accordingly.

National Insurance When You Are Both Employed and Self-Employed

National Insurance gets its own section because it works differently from income tax when you have both employment and self-employment income.

Through employment (Class 1 NI)

Your employer deducts Class 1 National Insurance from your salary. For 2025/26, the employee rate is 8% on earnings between £12,570 and £50,270, and 2% above that. Your employer also pays employer's NI on top.

Through self-employment (Class 2 and Class 4 NI)

On your freelance profits, you pay:

Class 2 NI: £3.45 per week (if profits exceed £12,570)
Class 4 NI: 6% on profits between £12,570 and £50,270, and 2% above that

How they interact

Here is the important bit: Class 1 NI from your employment and Class 4 NI from self-employment are calculated separately, but there is a maximum annual NI contribution. If you are paying significant NI through both employment and self-employment, HMRC will make sure you do not pay more than the combined maximum.

In practice, if your employment salary is above £50,270, you are already paying the higher rate of NI on your salary (2%). Your Class 4 NI on freelance profits would then be calculated accordingly. HMRC adjusts this automatically through your Self Assessment.

For most people freelancing on the side, the NI calculations are handled correctly on the Self Assessment return without any manual intervention needed. For a thorough explanation of the NI classes, see our guide on National Insurance when employed and self-employed.

Filing Your Self Assessment

When you have both employment and freelance income, you file a Self Assessment tax return each year. Here is the timeline:

Tax year: 6 April to 5 April
Registration deadline: By 5 October after the end of the tax year
Online filing deadline: 31 January following the end of the tax year
Payment deadline: 31 January (same as filing)

On your return, you will declare:

Your employment income (using the P60 your employer provides)
Your freelance income and expenses (on the self-employment pages)
Any other income (savings interest, dividends, rental income, etc.)

HMRC calculates the total tax owed, subtracts what has already been paid through PAYE, and tells you the difference. That difference is your Self Assessment tax bill.

If your total bill for the year exceeds £1,000, HMRC will also require you to make payments on account — advance payments towards next year's tax bill, each equal to half the current year's bill.

A first-time filer?

If you have never completed a Self Assessment before, it can seem daunting. Our first-time Self Assessment guide takes you through every section.

What Expenses Can You Claim?

Claiming expenses is one of the biggest advantages of being registered as self-employed. Every legitimate business expense reduces your taxable profit — and therefore your tax bill.

Common expenses for freelancers include:

Technology and equipment

Laptop, tablet, or desktop computer (business-use proportion)
Software subscriptions (design tools, project management, accounting)
Domain names and web hosting
External hard drives, monitors, peripherals

Home office

A proportion of household costs (rent/mortgage interest, council tax, utilities, insurance) based on the space and time used for freelancing
Or HMRC's simplified flat rates: £10/month (25–50 hours), £18/month (51–100 hours), £26/month (101+ hours)

Travel

Mileage to client meetings at 45p per mile (first 10,000 miles)
Public transport fares for business travel
Parking fees for business purposes

Professional costs

Professional body memberships
Training and development courses (if related to your current freelance work)
Professional indemnity insurance
Accountancy and bookkeeping fees

Marketing and sales

Website design and maintenance
Business cards and printed materials
Advertising (Google Ads, social media ads)
Portfolio hosting

Communication

Business phone contract or the business proportion of your personal phone
Business proportion of broadband
Video conferencing subscriptions

Administrative

Stationery and office supplies
Postage
Bank charges on a business account

Keep records and receipts for everything. HMRC requires you to retain them for at least five years after the 31 January filing deadline.

Penny, the AI bookkeeping assistant in Accounted, can categorise your freelance expenses automatically as they come through your bank account — which is a significant time-saver if you are juggling a full-time job and a freelance business.

Tax Code Changes — Will Your Employer Know?

A common concern is whether your employer will find out about your freelancing. The short answer is that HMRC does not notify your employer about your Self Assessment or your freelance income. Your return is confidential.

However, there is one indirect way your employer might notice: your tax code.

If you owe a relatively small amount of additional tax (under £3,000), HMRC may collect it by adjusting your PAYE tax code for the following year. This means your employer would see a different tax code — for example, instead of 1257L, it might be reduced to reflect the additional tax. Your employer can see that your code has changed, but they cannot see why. It could be for any number of reasons (savings interest, benefits in kind, underpaid tax from a previous year, etc.).

If you prefer HMRC not to adjust your tax code, you can opt out of this on your Self Assessment return and instead pay the full amount through Self Assessment. This keeps your PAYE completely separate.

Practical Tips for Freelancing Alongside Your Job

1. Check your employment contract

Many employment contracts include clauses about outside work. These might require you to:

Inform your employer about any secondary employment or freelance work
Get written permission before freelancing
Avoid working for competitors or clients of your employer
Ensure freelance work does not interfere with your primary role

Breaching these terms could result in disciplinary action, so it is worth reading the fine print. Some employers are very supportive of side projects; others are less so.

2. Separate your finances

Open a dedicated bank account for your freelance income and expenses. This makes bookkeeping infinitely easier and ensures you never confuse personal and business transactions.

3. Set aside money for tax

Your employer handles tax on your salary, but nobody is setting aside tax on your freelance earnings. A good rule of thumb is to save 25–30% of your freelance profit for tax and NI. Pop it in a savings account and do not touch it.

4. Invoice properly

Create professional invoices for your freelance clients. Each invoice should include your name, address, UTR number, the client's details, a description of the work, the amount, and the date. If you are not VAT-registered, you should not charge or show VAT on your invoices.

5. Track your time

When you are freelancing alongside a job, time is your most precious resource. Track how many hours you spend on freelance work — not just for billing clients, but also for claiming home office expenses (which are based on hours worked from home).

6. Plan for payments on account

If your first Self Assessment bill is significant, remember that you will also need to make payments on account for the next year. Your first January bill could be 150% of one year's tax (the full current year plus 50% advance for next year). This catches many new freelancers off guard.

VAT — Is It Relevant?

You only need to register for VAT if your taxable turnover exceeds £90,000 in a rolling 12-month period. For a side freelancer, this is unlikely — but not impossible if you are in a high-value field (consulting, development, design) and taking on substantial projects.

If you do hit the threshold, you would charge VAT on your freelance invoices (usually 20%) and submit quarterly VAT returns. Your employment income does not count towards the VAT threshold — only your self-employed turnover.

When to Consider Going Fully Freelance

There comes a point for many side freelancers when the question shifts from "how do I handle tax on my side income?" to "should I go full-time freelance?"

Some signs it might be time:

Your freelance income is matching or exceeding your salary
You have a consistent pipeline of clients
You have built up 3–6 months of expenses as a financial cushion
The administrative burden of two income streams is becoming unwieldy
You feel constrained by your employment contract

The tax implications of going fully self-employed are different — you will use more of your personal allowance, your NI situation changes, and you may want to consider whether a limited company structure is more tax-efficient. But that is a topic for another article.

Key Takeaways

If your freelance income exceeds £1,000, register as self-employed and file a Self Assessment.
Your freelance profit is added to your employment income for tax purposes.
You can claim legitimate business expenses to reduce your taxable profit.
National Insurance from employment and self-employment is calculated separately but capped.
Keep finances separate, save for tax, and check your employment contract.
Payments on account may apply from your second year of Self Assessment.

Freelancing alongside a full-time job is a brilliant way to grow your income, build skills, and test the waters of self-employment. The tax side is manageable — it just takes a bit of organisation and forward planning.

Accounted helps UK sole traders stay on top of their bookkeeping and tax. Start your free 30-day trial at getaccounted.co.uk

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