Annual Leave vs Sick Leave: What UK Employers Need to Know

Introduction

For UK employers, understanding the legal distinction between annual leave and sick leave is not just an HR nicety — it is a statutory obligation. The two types of absence are governed by different regulations, carry different pay requirements, and interact in ways that often trip up growing teams.

Annual leave is governed by the Working Time Regulations 1998, which entitle most workers to 5.6 weeks of paid leave per year. Sick leave is governed by the Statutory Sick Pay (SSP) regulations, which set out when and how employers must pay employees who are unable to work due to illness. Mixing up the rules for either can lead to underpayment, compliance breaches, and employment tribunal claims.

This guide explains the key legal differences, how annual leave and sick leave interact when an employee falls ill during or near a booked holiday, and what practical policies UK employers should have in place to stay compliant.

Statutory annual leave: the legal foundation

Under the Working Time Regulations 1998, most UK workers are entitled to 5.6 weeks (28 days for a five-day week) of paid annual leave per year. This is the statutory minimum — many employers choose to offer more as a competitive benefit. Part-time workers receive a pro-rata equivalent.

Key obligations for employers include:

• Ensuring every worker takes their statutory minimum leave each year
• Paying annual leave at the employee's normal rate of pay (including regular overtime and commission in some cases)
• Setting a clear leave year and communicating it to employees
• Managing carry-over in line with legal limits — up to 1.6 weeks (8 days) can be carried forward by default, more if the employee was on sick leave
• Keeping accurate records of leave taken and remaining

Annual leave is a positive right — employees choose when to take it (subject to employer approval), and employers cannot force workers to forgo their entitlement. Unlike sick leave, annual leave is planned and scheduled in advance through a request and approval process.

For a deeper look at setting up annual leave policies, see our annual leave policy checklist for growing teams.

Statutory sick leave: what the law requires

Sick leave is fundamentally different from annual leave. It is unplanned, unscheduled, and triggered by the employee's inability to work due to illness or injury. The legal framework centres on Statutory Sick Pay (SSP), which employers must pay to eligible employees who are off sick for at least four consecutive days (including non-working days).

Key facts about SSP:

• SSP is paid at a flat weekly rate set by the UK government
• It applies from the fourth consecutive day of sickness (the first three are “waiting days”)
• SSP can be paid for up to 28 weeks
• Employees must earn at least the Lower Earnings Limit to qualify
• Employers can recover some SSP costs from HMRC in certain circumstances

Many employers offer company sick pay (occupational sick pay) as a contractual benefit that supplements or replaces SSP. This is not a legal requirement but is common in competitive industries. Whatever your policy, it must be clearly documented and applied consistently.

Unlike annual leave, sick leave does not require employer approval — the employee notifies you they are unwell, and you follow your sickness absence procedure. However, employers can implement fit notes (formerly sick notes) and return-to-work interviews to manage long-term or frequent absences.

Key legal differences at a glance

The table below summarises the most important legal distinctions between annual leave and sick leave for UK employers:

How annual leave and sick leave interact

The interaction between annual leave and sick leave is one of the most commonly misunderstood areas of UK employment law. Here are the three scenarios every employer needs to understand:

1. Employee falls ill during annual leave

If an employee falls sick while on annual leave, they can self-certify and notify you that they are ill. In this case, the period of illness should be recorded as sick leave, and the annual leave days can be reclaimed for use later. This is established by UK case law (most notably the Pereda and Shah decisions) and aligns with ACAS guidance.

Your policy should set out:

• The notification process — how and when employees must tell you they are ill
• Whether you need self-certification or a fit note
• How reclaimed annual leave days can be rescheduled
• Whether there is a minimum period of illness before annual leave is reclaimed (common: full day or half day)

2. Annual leave during long-term sickness

Employees on long-term sick leave continue to accrue annual leave throughout their absence. They are entitled to take that annual leave either while still on sick leave or after returning to work. Crucially, if the employee was unable to take annual leave due to sickness, they can carry it over into the next leave year — there is no statutory cap on carry-over in this scenario.

The 18-month rule (from EU-derived law) means that annual leave accrued during long-term sickness can be carried over for up to 18 months following the end of the leave year in which it was accrued. After that point, the leave may be lost. Employers should track this carefully to avoid unexpected payouts when the employee eventually leaves.

3. Returning from sick leave and requesting annual leave

Employees returning from sick leave can request annual leave through the normal process. Employers should handle these requests fairly and consistently, taking into account any phased return or occupational health recommendations. Denying annual leave to someone returning from sickness could be seen as unreasonable and may lead to grievances.

Common compliance pitfalls

Even experienced HR teams make mistakes in this area. Here are the most common compliance pitfalls and how to avoid them:

Not recording sick leave separately from annual leave

Some employers record all absence in a single spreadsheet or calendar, mixing sick days with annual leave. This obscures absence patterns, makes it impossible to manage SSP correctly, and can lead to underpayment or overpayment of holiday pay. Always record sick leave and annual leave separately.

Failing to allow carry-over for sickness-related leave

Many employers apply a blanket “use it or lose it” policy, unaware that employees who were sick during the leave year have a statutory right to carry over unused annual leave. This can result in unlawful deductions from wages claims at tribunal.

Ignoring the “falling sick during holiday” policy

Without a clear written policy on what happens when an employee falls sick during annual leave, you risk inconsistent treatment — some managers may allow reclaiming of days, others may not. This inconsistency can lead to grievances and discrimination claims.

Miscalculating SSP waiting days

SSP is not payable for the first three consecutive days of sickness (the waiting days). Some employers mistakenly pay SSP from day one, while others incorrectly delay payment. Both errors create payroll complications and potential HMRC penalties.

Not tracking accrual during long-term sick leave

Annual leave continues to accrue while an employee is on long-term sick leave. Failing to track this can result in a large accrued leave liability when the employee returns or resigns. Dedicated leave management software automates this tracking and prevents surprises.

Best practices for managing both leave types

Here are practical steps UK employers can take to manage annual leave and sick leave correctly, reduce compliance risk, and build trust with their teams:

1. Document your policy clearly

Write a clear leave policy covering annual leave entitlements, the approval process, carry-over rules, sick leave notification procedures, SSP eligibility, and what happens if someone falls sick during annual leave. Share it with all employees and include it in your employee handbook. For help structuring this, see our leave management implementation playbook.

2. Use a system that separates leave types

Spreadsheets make it all too easy to mix annual leave and sick leave records. A dedicated leave management system keeps the two separate by default, calculates balances automatically, and provides an audit trail for every absence. This saves time and reduces errors.

3. Train managers on the differences

Managers are the first line of contact for leave requests and sickness notifications. Make sure they understand the legal differences between annual leave and sick leave, know how to handle reclaiming annual leave days during illness, and can spot potential compliance issues before they escalate.

4. Audit your records regularly

Review leave records quarterly to ensure annual leave and sick leave are recorded correctly, carry-over balances are accurate, and SSP payments are correct. Regular audits catch small errors before they become big compliance problems. For guidance on improving your process, read our article on reducing leave admin time.

5. Keep up with legal changes

Employment law evolves. The calculation of holiday pay, the treatment of carry-over, and SSP rates all change periodically. Subscribe to ACAS updates, review government guidance, and ensure your policies and software stay current.

Frequently asked questions