Zero-Hours vs Fixed-Term Contracts in the UK: Key Differences Explained

A zero-hours contract is an agreement where the employer is not obliged to provide any minimum hours, and the worker is generally not obliged to accept the work offered. It suits genuinely variable demand — such as hospitality cover or event staff — where shifts rise and fall week to week.

Despite the name, zero-hours workers are not without protection. They are entitled to at least the National Minimum Wage for hours worked, statutory holiday pay, rest breaks under the Working Time Regulations 1998, and protection from unlawful discrimination. They are also eligible for Statutory Sick Pay (SSP) — since 6 April 2026, SSP is payable from the first day of illness and the former Lower Earnings Limit has been abolished, meaning more zero-hours workers now qualify. What zero-hours workers lack is any promise of work — that is the defining feature of the arrangement.

GOV.UK guidance on zero-hours contracts and employer responsibilities sets out these duties in full.

Employment status also matters here. A zero-hours individual may be a worker or, depending on the facts, an employee — and that classification affects which rights apply. The label on the paperwork does not settle it; what counts is how the relationship works in practice, including whether the person must accept shifts and how much control you have over their work.

This distinction also affects how you handle PAYE and National Insurance contributions: workers and employees are both subject to standard deductions, but getting the status wrong can create unexpected tax liability for the employer. The ACAS guidance on zero-hours contracts is a practical reference for getting this classification right.

A fixed-term contract is an employment contract that ends on a specified date, on completion of a particular task, or when a defined event occurs — such as the return of an employee on maternity leave. Unlike zero-hours working, it comes with agreed hours and a clear start and end.

Fixed-term employees have broadly the same rights as comparable permanent staff, under the Fixed-term Employees (Prevention of Less Favourable Treatment) Regulations 2002. They must receive equal pay and benefits, access to the same facilities, and information about permanent vacancies. Our guide to fixed-term contract rights and limits explains these protections and the point at which repeated renewals can turn a fixed-term role permanent.

The three defining features of a fixed-term contract are:

1. Defined duration. The contract has a clear end point agreed in advance.
2. Equal treatment. Comparable rights, pay and benefits to permanent employees — including access to the same pension scheme, training opportunities and bonus arrangements.
3. Notice on early termination. Ending a fixed-term contract early usually requires notice and a valid reason; it cannot be treated as a cost-free exit.

The clearest way to see the differences is side by side. The distinction turns on whether hours are guaranteed and whether the contract has a fixed end.

Both differ again from agency work, where a third party employs the worker and supplies them to you — under a separate framework, the Agency Workers Regulations 2010. Our guide to the differences between fixed-term, temporary and freelance agreements untangles these overlapping categories, which are easy to mix up.

Each contract type carries real trade-offs for employers and workers alike.

• Zero-hours advantages: Maximum flexibility to match staff to demand, with pay only for hours worked. Useful for businesses with genuinely unpredictable workloads where committing to fixed hours in advance is not realistic.
• Zero-hours disadvantages: Unpredictable income for workers and weaker loyalty, plus growing legal scrutiny — particularly with the Employment Rights Act 2025 tightening the rules. Workers on zero-hours arrangements may also find it harder to secure mortgages or credit, which can affect recruitment and retention over time.
• Fixed-term advantages: Certainty for a defined period, useful for maternity cover, project delivery or a known busy season — the employer and worker both know where they stand from day one.
• Fixed-term disadvantages: Less flexibility mid-term, and repeated renewals can create permanent status. If a fixed-term employee reaches four years of continuous service without objective justification for the arrangement, they may acquire permanent employee rights automatically under the Fixed-term Employees (Prevention of Less Favourable Treatment) Regulations 2002.

The distinction matters a great deal for pay and benefits day to day. A fixed-term employee must not be treated less favourably than a comparable permanent colleague — withholding a bonus, training or benefits that others receive can itself be unlawful unless you can objectively justify it.

Zero-hours workers accrue holiday pay based on the hours they actually work, which takes some care to calculate correctly across variable shifts. Since April 2024, workers on irregular hours can be paid rolled-up holiday pay — 12.07% added to each payslip — which simplifies administration but must be clearly set out in the contract. Both categories also fall within PAYE and National Insurance requirements from the first pound earned.

These are exactly the details tribunals examine, and small administrative errors here are a common route to an avoidable claim.

The right contract follows the genuine shape of the work — not the other way around. Choosing to suit administrative convenience rather than operational reality is where employers get caught out.

Use a zero-hours contract when demand is genuinely unpredictable and you cannot promise hours in advance — covering event peaks, seasonal surges or ad hoc shifts. Use a fixed-term contract when you know you need someone for a defined period but not permanently — covering maternity leave, delivering a specific project or handling a known busy season.

• Choose zero-hours when the volume of work varies week to week and cannot be forecast
• Choose fixed-term when you need reliable cover for a known, time-limited period
• Choose permanent when the role is ongoing and the hours are predictable

Both contract types attract myths that lead employers into mistakes. Clearing them up protects everyone.

"Zero-hours workers have no rights." False. They are entitled to the National Minimum Wage, holiday pay, Working Time Regulations protections, and SSP from the first day of illness (since April 2026). Protection from unlawful discrimination also applies from day one.

"A fixed-term contract can be ended freely on the end date." Not quite. Expiry counts as a dismissal in law, so a fair process and notice may still apply — and an employee with two or more years' continuous service may be entitled to statutory redundancy pay if the reason for non-renewal is redundancy.

"Zero-hours and casual mean the same as agency work." No. Agency workers are supplied by and usually employed by a third party, under the Agency Workers Regulations 2010 — a separate framework with its own rights after a 12-week qualifying period.

The biggest change on the horizon is the Employment Rights Act 2025, which will end what the government calls "one-sided flexibility". According to the official GOV.UK implementation timeline, the reforms give qualifying workers a right to:

• Guaranteed hours that reflect the hours they actually work over a reference period
• Reasonable notice of shifts before they start
• Compensation when shifts are cancelled or curtailed at short notice

The Employment Rights Act 2025 also introduces a new concept: the low hours contract — covering workers who are on fixed (but very low) contracted hours that do not reflect the hours they actually work. These workers will benefit from the same guaranteed hours offer as zero-hours workers, meaning employers can no longer use minimal contracted hours as a workaround to avoid the reforms. This is a significant development for sectors such as retail, care and hospitality where low-hours contracts have been used as an alternative to zero-hours arrangements.

These measures, including their extension to agency workers, are expected to take effect in 2027, with the exact timing and detail to be set out in later regulations following consultation. All future dates remain subject to parliamentary processes. Employers who rely heavily on zero-hours staff should start reviewing their contracts now rather than waiting for the rules to bite. For smaller employers, our guide to UK employment law for small businesses is a useful grounding in the wider framework.

Preparing early is straightforward. Start by identifying which of your staff are on zero-hours or low-hours contracts and how many hours they typically work, so you can see who would qualify for guaranteed hours under the new regime.

Whichever route you choose, the paperwork should reflect the reality of the arrangement on the ground. A contract that promises guaranteed hours the person never actually receives, or a fixed-term label placed on what is really an open-ended role, creates exactly the mismatch that tribunals look for. Keep the written terms, the hours you offer and the day-to-day practice aligned — and revisit the contract whenever the pattern of work changes so the document and the reality never drift apart.

If predictability becomes important to your staff, a permanent contract may be the cleaner answer. Our permanent employment contract guide explains what that involves.

Choosing between a zero-hours and a fixed-term contract comes down to one question: do you need open-ended flexibility, or certainty for a defined period? Both carry real employment rights, and with the Employment Rights Act 2025 tightening the rules on zero-hours and low-hours working from 2027, the cost of getting it wrong is rising.

Match the contract to the genuine nature of the work, document it properly, and revisit it whenever the working pattern changes. Clear, well-signed contracts protect both employer and worker — and issuing them promptly, with a secure record of who signed and when, is one of the simplest forms of legal risk management available.