Can I Be Employed and Self-Employed at the Same Time?

Quick answer

Yes. There’s no conflict, no special permission needed, and HMRC handles both incomes through a single tax system. Millions of people in the UK have a day job and run a side business simultaneously.

Here’s how it actually works. This guide is part of our getting started series for new sole traders.

How tax works when you’re both

Your employer handles your employment income through PAYE — they deduct Income Tax and National Insurance before you receive your pay. That doesn’t change.

Your self-employed income goes through Self Assessment. Once a year (by 31 January), you file a tax return declaring your self-employed profits alongside your employment income. HMRC calculates the total, works out what you owe on the self-employed portion, and sends you a bill.

In practice, this means:

• Your personal allowance (£12,570) is usually used up by your salary — so your self-employed profits are typically taxed from the first pound
• You pay 20% Income Tax on self-employed profits if your total income is under £50,270
• You pay Class 4 National Insurance (6%) on self-employed profits above £12,570
• You pay Class 2 National Insurance (£3.45/week) — a flat rate regardless of profit level

Quick example

You earn £30,000 from your day job and £8,000 profit from a side business.

• Your employer already handles tax on the £30,000 via PAYE
• Your personal allowance (£12,570) is already used by your salary
• Your £8,000 self-employed profit is taxed at 20% = £1,600 Income Tax
• Class 4 NI on £8,000 at 6% = £480
• Class 2 NI: ~£179 for the year
• Total extra tax on the side business: ~£2,259

You’d pay this via Self Assessment by 31 January following the end of the tax year. Our sole trader tax guide has full rate tables and more worked examples.

Do I need to tell my employer?

HMRC won’t tell your employer about your self-employment. It’s your choice whether to disclose it.

However, check your employment contract. Many contracts include clauses about:

• Outside interests or secondary employment — some require you to notify your employer or get written permission
• Non-compete clauses — if your side business is in the same industry, your employer may object
• Working time regulations — in theory, you shouldn’t work more than 48 hours per week total (though you can opt out)

If your side business is in a completely different field — say, you work in marketing by day and sell candles on Etsy in the evenings — most employers don’t care. If it’s in the same industry, read your contract carefully.

When to register

The same rules apply as any sole trader. If your self-employed income exceeds £1,000 in a tax year, you need to register with HMRC. The £1,000 trading allowance applies to your self-employed income only — your salary doesn’t count toward it.

If you’re not sure whether you need to register, our guide on whether you need to register as self-employed covers all the edge cases.

Common concerns

“Will my employer find out through HMRC?” No. HMRC doesn’t notify employers about Self Assessment registrations. Your payslip won’t change. The only way your employer would find out is if you tell them, or if your self-employed income triggers a change to your PAYE tax code (which can happen if HMRC adjusts your code to collect Self Assessment payments — you can opt out of this by paying via lump sum instead).

“Will I pay too much tax?” Not if you file correctly. Self Assessment calculates your total liability across both incomes and accounts for tax already paid through PAYE. You only pay the difference. If your employer is already using your personal allowance, you won’t lose it twice.

“Can I claim expenses on my side business?” Absolutely. The same expense rules apply. Your home broadband, phone usage, equipment, travel — anything legitimately used for the side business can reduce your taxable profit. This is one of the advantages of registering properly.

“What if my side business makes a loss?” You can carry the loss forward to offset against future self-employed profits. In some cases, you can offset it against your employment income in the same tax year — though this is more complex. If you’re making consistent losses, speak to an accountant.

Setting aside money for tax

This is where most people with dual income get caught out. Your employer handles tax on your salary automatically. But the Self Assessment bill for your side business arrives in one lump in January — and it can be a surprise if you haven’t planned.

Set aside 25–30% of your self-employed income throughout the year. Open a savings pot in your business bank account and move money into it every time you’re paid. Monzo Business has automatic tax pots that do this for you; with other banks, do it manually.

After your first year of Self Assessment, HMRC may also ask for payments on account — two advance payments toward next year’s bill (each 50% of the previous year’s liability). This means in your second year, you could face three payments: the balance for year one, plus two payments on account for year two. Budget for this.

Next step

Ready to get started? Here’s the sequence:

1. Register as a sole trader — even if you already file a tax return for other reasons, you need to add self-employment to your HMRC record
2. Open a separate business bank account — essential when you have two income streams. Don’t mix them.
3. Set up accounting software — tracks your side business income and expenses separately from your salary
4. Start setting aside 25–30% of every self-employed payment into a tax savings pot

Last updated: March 2026. Tax rates and thresholds are for the 2025/26 tax year.