Let’s be real, lots of people are juggling two (or more!) jobs right now. Whether it’s driving for Deliveroo on Saturday nights, pulling weekend shifts at a warehouse, or doing a bit of freelance work on the side – moonlighting is basically the norm in 2026.

But here’s the thing: just because everyone’s doing it doesn’t mean a moonlighting job is automatically legal. And even if it is legal, there’s a sneaky tax trap that could land you with a surprise bill from HMRC, even when you’re earning well under the tax threshold.

You could be earning £10,000 a year across two jobs and still get overtaxed.
I’ll explain why in a minute, but first, let’s talk about whether your second job is even allowed in the first place.

Is Your Moonlighting Job Actually Legal?

Short answer: it depends on your contract.

In the UK, there’s no law that outright bans you from having a second job. However, your employer can include restrictions in your employment contract, and if you ignore them, you could be in breach of contract (which, in the worst-case scenario, means disciplinary action or even dismissal).

Check for “Exclusivity Clauses”

The big thing to look for is something called an exclusivity clause (sometimes called a “restrictive covenant”). This is a line in your contract that says you can’t work anywhere else without your employer’s written permission.

Here’s the good news: exclusivity clauses are now illegal for zero-hours workers in the UK, thanks to changes that came into force a few years back. So if you’re on a zero-hours contract and your employer tries to stop you from picking up shifts elsewhere, they’re breaking the law. You can read more about this on the ACAS website.

But if you’re on a permanent contract or a fixed-hours contract, your employer can include an exclusivity clause, and it’s perfectly legal for them to do so. That said, they can’t stop you from taking a moonlighting job “just because.” They need a legitimate reason, such as:

• Conflict of interest: You’re working for a direct competitor
• Health and safety: Your combined hours would breach the Working Time Regulations (which cap you at 48 hours a week on average unless you opt out)
• Performance concerns: Your second job is affecting your ability to do your main job properly

If you’re unsure whether your contract has restrictions, dig it out and give it a read. If there’s nothing in there about second jobs, you’re generally in the clear, but it’s always worth checking with HR or giving us a shout at Recruitment Robin if you need a second pair of eyes.

What About the Employment Rights Bill?

You might’ve heard about the Employment Rights Bill, which is rolling out new protections for workers in 2026. While it’s brought in some brilliant stuff (like day-one sick pay and stronger parental leave rights), it hasn’t drastically changed the rules around moonlighting.

What has shifted is the conversation around worker flexibility and employers being reasonable. The general vibe from employment tribunals and ACAS guidance is that blanket bans on a moonlighting job are becoming harder to justify, especially if your second job doesn’t actually interfere with your main role.

In short: if your employer says no to a second job, they need a proper reason. If they’re just being awkward, you might have grounds to push back.

The Tax Trap Nobody Warns You About

Right, this is where it gets proper annoying.

Let’s say you’ve got two part-time jobs — maybe you’re doing a 10am–2pm office shift in the day, then heading out for a 6pm–9pm cleaning shift in the evening. Your main job pays you £8,000 a year, and your second job pays you £4,000 a year. That’s £12,000 total: still under the personal tax allowance of £12,570, so you shouldn’t owe any tax, right?

Wrong.

Here’s what actually happens: HMRC automatically assigns your personal allowance (the £12,570 you can earn tax-free) to your main job. Your second job gets stuck with a BR tax code, which stands for “Basic Rate.” That means you’re taxed at 20% from the very first penny you earn, even though you’re nowhere near the actual tax threshold when you add both jobs together.

Why Does This Happen?

It all comes down to how the tax system works. HMRC doesn’t automatically know about your second job unless you (or your employer) tells them. When you start a new job, your employer sends your details to HMRC, and HMRC issues a tax code.

If it’s your first job, you’ll usually get a 1257L tax code, which gives you the full personal allowance. But if HMRC already has you registered with another employer, they’ll issue a BR code for the second job to avoid accidentally giving you two personal allowances (which would mean you’re not paying enough tax).

HMRC doesn’t automatically split your personal allowance between the two jobs. They just lump it all onto Job 1 and tax Job 2 at the basic rate. And, if neither job is paying you more than £12,570, you’re basically overpaying tax for no reason.

How to Fix It (And Get Your Money Back)

The good news? You’re not stuck with this. You’ve got two main options:

Option 1: Split Your Personal Allowance

You can ask HMRC to split your personal allowance between your two jobs. This is really easy to do via your Personal Tax Account on the GOV.UK website.

Here’s how:

1. Log in to your Personal Tax Account (you’ll need a Government Gateway ID)
2. Go to the “Pay As You Earn (PAYE)” section
3. Select “Update employer details”
4. Tell HMRC how much you expect to earn from each job
5. HMRC will recalculate your tax codes and send updated codes to both employers

Once that’s done, both jobs will tax you correctly, and you won’t overpay. Sorted!

Option 2: Claim a Refund at the End of the Tax Year

If you’ve already been overtaxed, you can claim it back. HMRC will usually review your tax automatically after the end of the tax year (5th April), and if you’ve overpaid, they’ll send you a refund cheque or transfer the money directly into your bank account.

But if you don’t want to wait, you can claim it back sooner by filling in a P50 form (if you’ve left one of the jobs) or a P53 form (if both jobs are ongoing). You can find these forms on GOV.UK.

Fair warning: HMRC can take a few weeks to process refunds, so don’t expect the money overnight!

What Should You Do Right Now?

If you’re working two jobs (or thinking about picking up a second one), here’s your action plan:

• Check your contract for exclusivity clauses. If you’re on zero hours, you’re golden. If not, see if your employer’s restrictions are actually reasonable.
• Sort out your tax code before you start getting paid from Job 2. Log in to your Personal Tax Account and let HMRC know about both jobs so they can split your allowance properly.
• Keep an eye on your payslips. If you’re seeing a BR tax code on your second job and you know you’re under the personal allowance, get in touch with HMRC straight away.
• If you’ve already been overtaxed, claim it back. Don’t just sit on it: HMRC won’t magically realise they owe you money unless you tell them.

And if you’re looking for flexible work that fits around your main job, give us a shout at Recruitment Robin.

Because honestly? Nobody should be getting done for tax when they’re just trying to make ends meet.