Should You Tell Your Boss About Your Side Hustle?
Around a quarter of UK workers have some kind of income coming in alongside their main job. A freelance project here, a small business there, something they’ve been quietly building on evenings and weekends. Maybe that’s you.
And if it is, there’s a good chance you’re sitting with a question at the back of your mind: do I need to tell my boss?
The honest answer is: it depends. But there are a few things worth checking before you decide — and a couple of things worth knowing regardless of what you choose.
Table of Contents
Check Your Employment Contract First
Before anything else, dig out your employment contract and read it properly. Some employers include clauses that restrict outside work — either requiring you to get written permission before taking on other paid work, or prohibiting it altogether in certain circumstances.
This isn’t as uncommon as people think, particularly in professional services, finance, or roles where there’s access to sensitive information or clients.
If your contract has a restriction clause, that doesn’t necessarily mean you can’t have a side hustle — it means you need to go through the right channels before you start. For most employers, a conversation or a written request is all it takes, unless what you’re planning creates a genuine conflict of interest.
If your contract has no such clause, you have more freedom — but it’s still worth thinking through the points below.
Is There a Conflict of Interest?
This is the question that matters most, and it’s worth being honest with yourself about it.
If your side hustle operates in a completely different space from your day job, you’re almost certainly fine. A project manager who makes ceramics at weekends, a nurse who does fitness coaching, an accountant who writes — these aren’t conflicts.
But if you’re using the same skills, the same network, or the same industry knowledge as your employer — particularly if you’re working with similar clients or in direct competition — that’s a conversation worth having proactively, rather than having it forced on you later.
You don’t need to share every detail. A broad outline is usually enough for HR to give you a steer on what’s acceptable. Getting clarity upfront protects you — and your job.
Think About Your Relationship With Your Boss
If you have a strong, trusting relationship with your manager, telling them can actually work in your favour. It shows confidence and integrity. It removes any awkwardness if it ever comes up. And some managers genuinely respect people who are building something outside work.
What no boss — however supportive — wants to find out is that your side hustle is eating into your working day. Making clear from the start that your side hustle stays outside work hours, and that your performance isn’t affected, tends to put people at ease.
If your relationship with your manager is more transactional, or you work somewhere that frowns on outside interests, you’re well within your rights to keep it to yourself — as long as there’s no contractual obligation and no conflict of interest.
Trust Your Gut
Some people genuinely don’t lose a wink of sleep over keeping their side hustle private. It’s their time, their project, their business — and as long as the contract’s clear, that’s a perfectly reasonable position.
Others feel that low-level anxiety of not having told them, and find that a brief, matter-of-fact conversation removes it entirely.
Neither approach is wrong. What matters is that you’ve checked the contract, thought honestly about conflicts, and made a deliberate choice — not just assumed it’ll be fine.
Don’t Forget the Tax Side
This is the bit people often overlook when they’re focused on the “should I tell my boss?” question.
If your side hustle earns you more than £1,000 in a tax year, you’re legally required to register with HMRC and declare that income through a Self Assessment tax return. This is completely separate from your employment — your employer doesn’t need to know, and it doesn’t affect your tax code at work (unless you ask HMRC to collect it that way).
What it does mean is that you need to track your side hustle income and expenses from day one, register with HMRC by 5 October following the tax year you started earning, and file a return by 31 January each year.
The good news: it’s more straightforward than most people expect once you’ve got the right systems in place.
Read => How to Register as Self-Employed in the UK
Read => Self-Employed Tax: How It Works and What You Need to Know
If you’re building a side hustle, The Self Employed Club was made for you. It’s a free, members-only platform with handpicked deals on the tools, software, and services UK sole traders actually use — from accounting software to business banking. Free to join, no catch. Join here →
The Bottom Line
Your side hustle is yours. You built it, you’re running it, and what you do outside work hours is — in most cases — your own business.
But a quick check of your contract, an honest look at whether there’s a conflict, and a decision made with clear eyes will always serve you better than ignoring the question and hoping for the best.
And when the side hustle starts to grow — when you’re thinking about going full time, or just want to make sure you’re keeping more of what you earn — The Self Employed Club is worth joining. Completely free, built specifically for UK sole traders, and full of deals that make self-employed life a bit less expensive. Join The Self Employed Club free →
FAQs
Do I legally have to tell my employer about my side hustle?
Only if your employment contract requires it. Check for clauses about outside work or secondary employment — if there’s a requirement for written permission, follow it. If there’s no such clause and there’s no conflict of interest, you’re not legally obliged to disclose it.
Can my employer stop me having a side hustle?
Potentially, if your contract prohibits outside work without permission. In practice, most employers are reasonable — especially if your side hustle doesn’t compete with their business. If permission is required, it’s usually better to ask than to assume.
What if my side hustle is in the same industry as my day job?
Tread carefully. Using the same skills is usually fine; approaching your employer’s clients or competing directly is not. A conversation with HR to get clarity upfront is worth it — it protects you as much as it protects them.
Do I need to tell HMRC about my side hustle income?
Yes — if you earn more than £1,000 from your side hustle in a tax year, you must register with HMRC and declare it on a Self Assessment tax return. Here’s how to register →
Will my employer find out about my side hustle through my taxes?
No — your Self Assessment return is between you and HMRC. Your employer won’t be notified unless you ask HMRC to collect any underpaid tax through your PAYE tax code, which you can choose not to do.
What tools do I need to run a side hustle alongside a day job?
At minimum: a way to track income and expenses, and a business bank account to keep things separate. The Self Employed Club has free membership and deals on exactly the tools you need. Join free →
Want to Read More About Sole Trader Life?
If you’ve enjoyed this post you may like to read more about sole trader life? Here are some of my most popular blog posts on this topic…
Join the Club — it's completely free
Members get handpicked deals and discounts on the tools, services and everyday essentials UK sole traders actually use. Free to join, no catch.