Do I Need to File a Tax Return If I'm Employed and Self-Employed?

The short answer

• ✓ Over £1,000: if your self-employed income is more than £1,000 in a tax year, before expenses, you need to register for Self Assessment and file a return. Having a job taxed through PAYE doesn't change that.
• ✓ £1,000 or less: the trading allowance usually covers it, and you don't need to register for that income alone.
• ✓ Deadline to register: 5 October after the end of the tax year. For the 2025/26 tax year, that's 5 October 2026.
• ✓ How it's taxed: your side profit is added on top of your salary, so it's taxed at your highest rate, not your lowest.

All figures in this article were checked against GOV.UK on 1 October 2026. Income Tax rates are for England, Wales and Northern Ireland. Scotland has its own Income Tax bands.

Does being on PAYE mean you don't need to file?

No. PAYE only covers the pay your employer gives you and takes tax from. It can't see anything you earn outside that job: freelance work, a side business, consultancy or content creation.

HMRC doesn't know about that income unless you tell it, and registering for Self Assessment is how you tell it. Many people assume their payslip has "sorted" their tax. It has, but only for the job.

How does the £1,000 trading allowance work?

The trading allowance lets you earn up to £1,000 of gross self-employed income a year tax-free. You don't need to register or report it, as long as you have no other reason to file a return.

HMRC's guidance on the trading allowance has the full rules. These are the points that catch people out:

• ✓ It's based on gross income, before expenses, not profit. £1,000 of turnover is £1,000, even if your actual costs were minimal.
• ✓ The moment your gross self-employed income goes over £1,000 in a tax year, you need to register with HMRC by 5 October following the end of that tax year.
• ✓ Once you're above the threshold, you choose between the trading allowance or deducting your actual expenses, whichever is higher, you can't use both on the same income.
• ✓ You can't use the allowance on income from your own employer, your spouse's or civil partner's employer, or a company or partnership you're connected to. Doing extra work on the side for your day-job employer doesn't qualify.
• ✓ If your self-employed venture made a loss, you may want to report it anyway rather than rely on the allowance, since a loss can sometimes be offset against other income. Worth a proper conversation rather than assuming either way.

When do you need to register for Self Assessment?

If you go over the £1,000 threshold, you need to register for Self Assessment by 5 October after the end of that tax year. For 2025/26, that's 5 October 2026. Register late and you could get a penalty.

If you're doing this for the first time, our first Self Assessment checklist walks through registration, getting your UTR, and what to gather before you file.

What does your tax return cover once you register?

This surprises people most. Your return doesn't cover the side income on its own. It asks for your employment income too, using the figures from your P60.

HMRC then works out the tax on your total income and credits you with the tax already taken through PAYE.

Two practical consequences follow from this:

• ✓ Your Personal Allowance is shared across both income sources, not doubled. It's already largely used up by your salary in most cases, meaning your self-employed profit is often taxed close to its full rate from the first pound.
• ✓ Stacking self-employed profit on top of a salary can push part of your combined income into a higher tax band than either income would reach alone. This is the single biggest reason people underestimate what they owe.

An illustrative example for 2026/27

Say you earn a £45,000 salary and make £10,000 profit on the side. The £10,000 is taxed as the top slice of £55,000, and the higher rate threshold is £50,270.

• ✓ £5,270 of the profit is taxed at 20%: £1,054
• ✓ The other £4,730 is taxed at 40%: £1,892
• ✓ Income Tax on the side profit: £2,946, an average of about 29%

There's no Class 4 National Insurance in this example. It's worked out on your self-employed profit alone, and it only starts above £12,570 of profit, according to HMRC's self-employed National Insurance rates.

The example is illustrative. It assumes no other income, no pension contributions and no student loan.

What are the most common mistakes to avoid?

Most problems in this situation come from assumptions rather than the tax rules themselves:

• ✓ Assuming PAYE "covers" everything because tax is already being deducted from a payslip
• ✓ Missing the 5 October registration deadline because the side income crept over £1,000 without anyone noticing
• ✓ Not keeping separate records for the self-employed side, then struggling to reconstruct income and expenses months later
• ✓ Claiming the £1,000 trading allowance on extra work done for your own employer, which isn't allowed
• ✓ Underestimating the tax bill by mentally taxing the self-employed income on its own, rather than as an addition to an existing salary

Keeping the two income streams cleanly separated from day one avoids most of this. Our bookkeeping service can help set that up properly even if the self-employed side is small for now.

The bottom line

If your side income is over £1,000 a year, you need a tax return, whatever your job pays. Register by 5 October after the tax year ends, keep the side business's records separate, and budget for the tax at your top rate, not your lowest.

How REYS Accountants can help

We're a small practice in Catford, SE6, and side income on top of a salary is one of the most common situations we see.

Our Self Assessment service works out what you owe once both incomes are combined, registers you if needed and files the return.

If you're a higher earner, our page on personal tax for Forest Hill and Honor Oak covers side income alongside the £100,000 allowance trap. Get in touch and we'll tell you plainly where you stand.

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