Can You Work a Second Job While on Stress Leave? UK Employer Risks & HR Steps

As a small business owner or manager, stress-related absences can be tricky to handle. You want to support your employee, keep your team running, and stay legally compliant - all at the same time.

One situation that often throws employers is this: your employee is signed off work with “stress” or “work-related stress”… but you find out they’re doing a second job (or gig work) while they’re off.

So, can an employee work a second job while on stress leave in the UK? And more importantly for you as an employer: what are your legal risks, and what steps should HR take so you respond fairly and safely?

Let’s break it down in plain English.

Is It Illegal For An Employee To Work A Second Job While On Stress Leave?

In most cases, it’s not automatically illegal for an employee to do another job while they’re off sick with stress.

But (and it’s a big but), it can still create serious issues for you and your business depending on:

• What their fit note (“sick note”) says and what they told you about their condition
• What the second job involves (physical work, high-pressure work, similar role to yours, etc.)
• Whether the second job conflicts with your business (competition, use of confidential info, working for a client/supplier)
• Whether they’re receiving sick pay (company sick pay or SSP) and whether working elsewhere undermines the basis for it
• Whether their stress is said to be “work-related” and whether they’re claiming your workplace caused it

From an employer perspective, the key point is: stress leave doesn’t automatically mean “can’t do any work at all.” Some employees may genuinely be unable to work in your environment (for example, due to workplace triggers, conflict, bullying allegations, workload, or anxiety connected to their role), but still be able to do other work that feels lower pressure or more flexible.

So when employers ask whether someone can work a second job while on stress leave, the real HR/legal questions are usually:

• Is the employee being honest about their capability?
• Are they acting in a way that breaches contract, policy, or trust and confidence?
• Are you handling this in a fair, evidence-based way?

Check Your Starting Point: Employment Contract And Policies

Before you jump to conclusions, check what you already have in place. Your Employment Contract and policies may cover:

• Rules on secondary employment / outside work
• Whether consent is needed for second jobs
• Conflict of interest restrictions
• Sick pay conditions (including company sick pay)
• General conduct expectations during sickness absence

If your paperwork is unclear or silent, that doesn’t mean you have no options - but it does mean you need to handle things carefully and consistently.

Why This Creates Legal Risk For Employers (Even If You’re “Right”)

This kind of situation can feel black-and-white in practice (“they’re off sick, but they’re working!”), but legally it’s often a grey area.

The main risks for employers usually come from how you respond, not simply the fact you’re concerned.

1) Unfair Dismissal Risk (If You Act Too Quickly)

If you dismiss or discipline without a fair process, you could be exposed to an unfair dismissal claim (if they have the qualifying service) or a dispute around breach of contract.

Even where you suspect misconduct, you generally need to:

• Investigate properly
• Put allegations to the employee
• Give them a chance to respond
• Follow a fair procedure consistent with ACAS guidance

In many cases, this situation is treated as a misconduct issue (dishonesty, abuse of sick pay, breach of trust) or a capability/absence management issue - but you need to choose the right track based on the facts.

2) Disability Discrimination Risk (Stress-Related Conditions Can Amount To A Disability)

Stress itself isn’t automatically a disability. However, an underlying mental health condition linked to stress (for example, anxiety, depression, PTSD or another condition) may be classed as a disability under the Equality Act 2010 if it has a substantial and long-term adverse effect on day-to-day activities.

If you mishandle the situation - for example, by making assumptions, refusing adjustments, or treating them unfavourably because of something arising from disability - you can create significant legal exposure.

This is why it helps to keep your response grounded in process and evidence, and to consider medical input where appropriate.

3) Data Protection And Privacy Problems (How You “Find Out” Matters)

Some employers discover second jobs through social media, clients, colleagues, or even CCTV. The information may be accurate - but you still need to think carefully about data protection and privacy, especially if you’re collecting, storing, or sharing information about an employee’s health or conduct.

In the UK, this is commonly governed by the UK GDPR and the Data Protection Act 2018. If workplace monitoring is part of the picture, make sure it’s covered by appropriate policies and that what you do is necessary and proportionate. This is a common trap area in investigations, particularly for small businesses without formal HR resources. Having an Acceptable Use Policy can help set expectations around systems and monitoring.

4) Sick Pay Disputes And Breach Of Contract Claims

If you provide enhanced company sick pay, your policy may allow you to withhold it in certain circumstances (for example, misconduct or failure to follow reporting rules). But you need to apply those rules consistently and fairly.

Even with SSP, you need to be cautious. Working another job doesn’t automatically stop SSP entitlement - but it can raise questions about whether they are genuinely incapable of work for you.

Any decision to stop company sick pay should be based on:

• Clear contractual/policy wording
• A fair investigation
• A documented decision-making process

Practical HR Steps: What To Do If You Suspect An Employee Is Working Elsewhere

If you suspect an employee is working a second job while on stress leave, the goal is to respond calmly, fairly and in a way you can justify later.

Here’s a practical step-by-step approach that usually works well for small businesses.

Step 1: Don’t Assume Misconduct - Start By Gathering Basic Facts

Before you invite the employee to any formal meeting, clarify what you actually know. For example:

• What is the source of the information?
• Is it reliable and specific (dates, times, role), or vague gossip?
• Could it be misunderstood (for example, volunteering, a one-off appearance, old photos)?

Keep a short written note of what you’ve been told and by whom. Avoid “digging” in a way that could breach privacy.

Step 2: Check The Fit Note And Your Sick Leave Records

Check what the medical evidence says and whether the employee is following your absence reporting process.

If you’re unsure what you can and can’t challenge, it helps to understand the limits around medical certificates. The topic comes up often in practice: sick notes are influential evidence, but employers still need to make operational decisions and can investigate inconsistencies.

Also be mindful that employees generally have privacy rights around health information. If you’re considering asking for more detail, make sure you approach it appropriately. Many employers find it helpful to revisit the principles around medical information and what’s reasonable to request.

Step 3: Hold A Welfare/Return-To-Work Style Conversation First (Where Appropriate)

In many cases, the best first move isn’t a disciplinary invite - it’s a welfare check-in.

You can ask neutral, non-accusatory questions like:

• How are you feeling at the moment?
• Is there anything about work that’s contributing to your symptoms?
• What support would help you return?
• Are you currently doing any other work, volunteering, or commitments that affect your availability or recovery?

This approach helps you:

• Show you’re acting reasonably and supportively
• Reduce the risk of escalating a sensitive mental health situation
• Test whether the employee is transparent

If they disclose a second job, you can then explore what it involves, whether it’s compatible with their recovery, and whether it creates any conflicts with your business.

Step 4: Decide Whether This Is Misconduct, Capability, Or Both

Not every “second job during stress leave” issue is the same. Common categories include:

• Misconduct: dishonesty, false sick leave, breaching a policy requiring consent for outside work, working for a competitor, misuse of confidential information
• Capability/health: the employee is unwell and cannot work for you, but may be fit for different work; focus is on adjustments, support, and return planning
• Mixed situation: the employee is unwell but has acted in a way that damages trust

Choosing the right route matters because it affects your process, your documentation, and the fairness of your outcome.

If the employee is likely to be off for a longer period, you may also need a structured long-term absence approach. It can be useful to align your handling with best practice around long-term sick leave, especially if the absence becomes prolonged and you’re considering next steps.

Step 5: If You Need A Formal Investigation, Keep It Proportionate

If the facts suggest dishonesty or a serious breach, move to an investigation.

At this stage, you should:

• Invite the employee to an investigation meeting (separate from a disciplinary hearing)
• Explain what the concern is and what evidence you have
• Give them a chance to respond
• Consider whether you need medical input (for example, occupational health) to assess capability

If the situation is serious enough to warrant suspension, it must be handled carefully and fairly (and kept under review). Long suspensions can cause their own legal and employee relations risks. If you’re unsure of the ground rules, it may help to revisit guidance on suspension pending investigation.

Step 6: Document Every Step

Good notes can make or break your position if the employee raises a grievance or brings a claim later.

Document:

• Absence dates and fit notes provided
• Welfare check-in attempts and outcomes
• Any disclosed secondary work and the employee’s explanation
• Investigation steps and evidence reviewed
• How you reached your decision (and why it was reasonable)

This is also where having a consistent staff handbook and clear policies is invaluable - it helps you show you treated the employee in line with known rules, rather than reacting emotionally.

Common Employer Scenarios (And How To Think About Them)

To make this more practical, here are a few common examples small businesses run into.

Scenario A: Employee Signed Off With Stress, But Works A Bar Job On Weekends

This may or may not be a problem. Key questions include:

• Does their fit note say “not fit for work” generally, or are there recommended adjustments?
• Is their stress related specifically to your workplace (for example, a managerial conflict)?
• Are they receiving enhanced sick pay from you?
• Does their contract require permission for other work?

Often, a welfare conversation is a sensible first step. If they’re open and the second job is genuinely different/less triggering, it may be manageable with clear boundaries.

Scenario B: Employee Claims Workload Stress, But Is Freelancing In The Same Industry

This tends to be higher risk.

It may suggest:

• They are not genuinely unfit for your role (capability question)
• They may be working for a competitor or soliciting clients (misconduct/restrictive covenant issue)
• They may be using your confidential information (serious misconduct risk)

This is usually where you’d consider a formal investigation and check your contract restrictions and confidentiality clauses.

Scenario C: Employee Is Off With Stress, Starts A Side Business, Posts About It Online

Social media posts can be misleading, but they can also provide genuine evidence.

Proceed carefully:

• Take copies/screenshots in case the content is deleted
• Don’t demand access to private accounts
• Focus on what is objectively visible and relevant

Your aim isn’t to “catch them out” - it’s to establish whether there is a genuine inconsistency that affects trust, pay, or workplace management.

How To Reduce The Risk In Future: Policies, Contracts, And Early Intervention

If you’ve dealt with this once, you’ll know it can quickly become time-consuming and stressful for the business.

A few preventive measures can significantly reduce your risk next time.

Put Clear Secondary Employment Rules In Writing

Many disputes happen simply because the business has no clear rule, or it’s inconsistently enforced.

Consider setting out:

• Whether employees need written consent before taking outside work
• How conflicts of interest are defined
• Whether working for competitors/suppliers/customers is prohibited
• Whether outside work is prohibited during working hours or sickness absence (and how this is assessed)

Have A Clear Sick Pay Policy

Make sure your documents are aligned on:

• When company sick pay applies (and when it can be withheld)
• Evidence requirements
• Rules on keeping in touch during sick leave
• Return-to-work meetings and fit note review

Train Managers On Mental Health Absence

Stress-related absence needs a slightly different approach than a straightforward short-term physical illness.

Training helps managers avoid:

• Accusatory language
• Pressure that could worsen symptoms
• Inconsistent decision-making
• Missing early warning signs (and allowing absence to drift)

Use Early, Structured Performance And Support Processes Where Relevant

Sometimes “stress leave” overlaps with performance issues, interpersonal conflict, or unclear role expectations. When an employee is struggling at work, early intervention and support can prevent a longer-term absence.

If performance management is part of the bigger picture, make sure you use a fair process. A well-run Performance Improvement Plan can be a practical way to set expectations while still supporting the employee.

Key Takeaways

• For most employees, it’s not automatically unlawful to work elsewhere while off sick. Whether an employee can work a second job while on stress leave will depend on the facts, the medical context, and any contractual or policy rules.
• The biggest risk for employers is acting too quickly or emotionally; you need a fair, evidence-based process before disciplining or dismissing.
• “Stress” is not automatically a disability, but it can be linked to a mental health condition that may qualify as a disability under the Equality Act 2010, so handle conversations and decisions carefully.
• Start with a welfare conversation where appropriate, then decide whether the issue is misconduct, capability, or a combination of both.
• Check your employment contract, sick pay terms, and policies on secondary employment/conflicts of interest before taking action.
• Document your steps and keep investigations proportionate to reduce the risk of unfair dismissal, discrimination, and pay disputes.
• Prevent future issues by tightening contracts and policies and training managers to handle mental health absences consistently.

This article is general information only and not legal advice. For advice on your specific situation, speak to an employment lawyer.

If you’d like help reviewing your employment contracts, sick pay policies, or managing a sensitive stress leave situation, you can reach us at 08081347754 or team@sprintlaw.co.uk for a free, no-obligations chat.