On-Call Work Rules UK: Employer Compliance 2026

On-call work sits at the intersection of working time law, pay compliance and health and safety risk. It is also one of the areas where employers most often get the legal analysis wrong, not through deliberate non-compliance, but through over-reliance on labels, legacy practices and assumptions that no longer withstand scrutiny.

The core legal framework is set by the Working Time Regulations 1998, supported by National Minimum Wage legislation and health and safety duties. Together, these regimes regulate how on-call time is classified, how long workers may lawfully work, when rest must be provided and when pay obligations arise.

UK employment law does not treat all on-call arrangements the same. Whether on-call time counts as working time, attracts pay, counts towards the 48-hour weekly maximum or disrupts statutory rest depends on the practical reality of the arrangement, not what the employer calls it in a contract or policy. Small differences in response time, location restrictions or freedom of movement can completely change the legal outcome.

For employers, mistakes in this area rarely remain isolated. A single misclassified on-call arrangement can trigger multiple exposures at once: breach of the Working Time Regulations 1998, unlawful deduction from wages, National Minimum Wage underpayment, health and safety enforcement and reputational damage if fatigue-related incidents occur.

What this article is about

This is a compliance-grade employer guide to on-call work rules in the UK. It explains how on-call arrangements are assessed under the Working Time Regulations 1998, when on-call time counts as working time, how pay and rest rights are affected, and how employers should structure on-call systems to withstand regulatory and tribunal scrutiny. The focus throughout is on defensible decision-making, not theoretical explanation.

Section A: What counts as on-call work under UK law?

On-call work is not defined as a single concept in UK employment legislation. There is no statutory definition of “on-call”, “standby” or “call-out” in the Working Time Regulations 1998. This absence of definition is deliberate. The law focuses on substance over form, requiring employers to assess how the arrangement operates in practice rather than how it is described in contracts or rotas.

From a legal perspective, on-call work broadly describes periods where a worker is not actively performing tasks but is required to be available to work if called upon. The compliance risk arises because this availability can range from minimal inconvenience to a level of restriction that is effectively indistinguishable from working time.

Employers often attempt to draw bright lines between “on-call”, “standby”, “sleep-in” and “shift” work. These labels may be useful for internal administration, but they do not determine legal status. Tribunals and enforcement bodies consistently disregard contractual labels if they do not reflect operational reality. The correct legal question is always whether the worker’s time is genuinely their own.

It is also important to be clear about coverage. The Working Time Regulations 1998 apply to “workers” broadly, not only employees. For most employers, this means the working time analysis will apply to employees and to many categories of casual staff and individuals engaged under worker arrangements, even where their contractual status differs.

Two broad categories of on-call arrangements tend to emerge in practice. In the first, the worker is free to remain at home or elsewhere of their choosing, subject only to being contactable and able to attend work within a reasonable time. In the second, the worker’s freedom is significantly constrained by location requirements, response times or activity restrictions imposed by the employer. It is this second category that creates the greatest compliance exposure.

The distinction matters because it determines whether on-call hours count as working time for the purposes of maximum weekly limits, rest entitlements and record-keeping obligations. It also influences whether the time must be treated as paid time under National Minimum Wage rules. Misclassifying these arrangements is one of the most common causes of enforcement action in working time cases.

Section A summary

UK law does not recognise “on-call” as a fixed legal category. Employers must assess on-call arrangements based on their practical impact on the worker’s freedom. Labels are legally irrelevant, and misclassification creates immediate working time, pay and health and safety risk.

Section B: When does on-call time count as working time?

Whether on-call time counts as working time is the central compliance question for employers. The answer determines exposure across working time limits, rest rights, record-keeping duties and, in many cases, pay liability. The Working Time Regulations 1998 define working time broadly as periods when the worker is working, at the employer’s disposal and carrying out their duties. How that definition applies to on-call arrangements has been shaped primarily through appellate authority and enforcement practice.

The starting point is the distinction between on-call at the workplace and on-call away from the workplace. Where a worker is required to remain at the employer’s premises, or at another place determined by the employer, the entire on-call period will almost always count as working time, even if the worker is permitted to rest or sleep when not responding to calls. The obligation to be physically present places the worker at the employer’s disposal for the full period.

On-call arrangements away from the workplace require closer analysis. In these cases, tribunals and regulators assess the degree of restriction placed on the worker during the on-call period. The legal question is whether the constraints imposed by the employer so limit the worker’s ability to manage their own time that the period should be treated as working time. This is a fact-sensitive assessment and not a simple binary test.

Factors that materially increase the likelihood that on-call time will count as working time include very short response times, requirements to remain within a narrow geographical area, restrictions on alcohol consumption, limitations on personal activities and a high frequency or unpredictability of call-outs. The more these factors apply, the more likely it is that the worker is considered to be at the employer’s disposal for the entirety of the on-call period, not just the time spent responding to calls.

Employers often focus solely on how often workers are called out. This is a compliance error. Even infrequent call-outs will not prevent on-call time being treated as working time if the underlying restrictions are severe. Conversely, genuinely low-impact availability arrangements, where the worker retains meaningful freedom and is rarely called upon, are more likely to fall outside working time except for the periods of actual work.

From a compliance perspective, this analysis must be undertaken proactively. Employers cannot wait until a dispute arises to decide whether on-call time counts as working time. If challenged by the Health and Safety Executive or in tribunal proceedings, the employer will be expected to evidence why the arrangement does not meet the legal test for working time.

Section B summary

On-call time counts as working time where the worker is required to remain at the workplace or where restrictions away from the workplace are sufficiently limiting. Employers must assess restriction levels in advance and cannot rely on call-out frequency or contractual wording to avoid working time classification.

Section C: How do on-call rules affect the 48-hour weekly limit and rest rights?

Once on-call time is classified as working time, its impact on statutory limits and rest rights follows automatically. This is where many employers encounter compounded risk, as breaches often arise across multiple obligations at the same time rather than in isolation.

Under the Working Time Regulations 1998, workers must not work more than an average of 48 hours per week unless a valid opt-out is in place. The average is normally calculated over a 17-week reference period, although this may be extended in certain sectors or by agreement. Where on-call hours count as working time, they must be included in this calculation in full.

Employers who exclude on-call hours on the assumption that they are “inactive” often discover, too late, that their workforce has been routinely exceeding the weekly maximum. The risk is particularly acute in sectors with layered rotas, such as healthcare, engineering, IT support and utilities, where on-call arrangements sit on top of standard shifts.

Rest rights present an even greater compliance challenge. Workers are entitled to a minimum of 11 consecutive hours’ daily rest and 24 hours’ uninterrupted weekly rest, or 48 hours per fortnight. On-call call-outs frequently interrupt these rest periods. Where rest is disrupted, employers must provide equivalent compensatory rest as soon as possible.

This obligation applies regardless of whether the worker has signed a 48-hour opt-out. Rest rights cannot be waived. Employers who assume that opt-outs neutralise rest obligations often find themselves in breach even where total weekly hours appear acceptable.

From a health and safety perspective, regulators increasingly treat inadequate rest as a systems failure rather than an individual choice. Employers are expected to manage fatigue risk proactively, particularly where on-call duties are frequent, unpredictable or combined with night work. Failure to do so exposes organisations to enforcement action even in the absence of a specific incident.

Section C summary

Where on-call time counts as working time, it must be included in the 48-hour weekly average calculated over the relevant reference period and actively managed to protect rest rights. Opt-outs do not remove rest obligations, and failure to manage fatigue creates regulatory and safety exposure.

Section D: Do employers have to pay for on-call time?

Whether on-call time must be paid is a separate question from whether it counts as working time, but the two are closely connected in practice. Employers frequently assume that if on-call time is not “active work”, it does not attract pay. This assumption is one of the most common sources of back-pay liability under National Minimum Wage legislation.

The National Minimum Wage framework looks at whether a worker is working, available for work or actually working during the relevant pay reference period. Where on-call time counts as working time because the worker is required to be at the employer’s disposal, that time will usually fall within the scope of payable hours for minimum wage purposes. This applies regardless of whether the worker is actively performing tasks throughout the period.

It is critical for employers to understand that minimum wage compliance is assessed pay reference period by pay reference period, not averaged across longer periods. A worker may therefore be underpaid in a particular pay period even if their average earnings appear compliant over time. This creates acute risk where on-call availability significantly increases payable hours without corresponding pay adjustments.

Sleep-in shifts have historically been a particular flashpoint. Earlier assumptions that sleep-in time could be treated as unpaid availability have been significantly narrowed by case law. The current position is that where a worker is permitted to sleep but is required to remain at a place specified by the employer and respond if needed, the legal analysis focuses on the level of obligation rather than the likelihood of being disturbed. Employers who rely on outdated guidance in this area remain exposed to substantial arrears claims.

On-call arrangements away from the workplace require careful assessment. Where the worker is genuinely free to use the time as they wish and is only paid for time spent responding to call-outs, minimum wage liability may be limited to those active periods. However, this position becomes increasingly difficult to defend as restrictions increase. Short response times, geographic constraints and activity bans can tip availability time into payable time.

Contractual arrangements do not override statutory minimums. Even where contracts specify flat-rate on-call allowances or exclude payment for certain periods, employers remain liable for minimum wage compliance across the total number of payable hours. Where this is overlooked, HMRC can require repayment of arrears going back up to six years, together with financial penalties and public naming.

Section D summary

On-call time that places a worker at the employer’s disposal is likely to be payable for minimum wage purposes. Compliance must be assessed pay period by pay period, and reliance on allowances or outdated sleep-in assumptions creates significant back-pay and enforcement risk.

Section E: What records must employers keep for on-call work?

Record-keeping is where many on-call compliance failures are ultimately exposed. Even where an employer believes its on-call arrangements are lawful, the inability to evidence how hours, rest and pay are managed can be enough on its own to trigger enforcement action.

Under the Working Time Regulations 1998, employers must keep adequate records to demonstrate compliance with weekly working time limits, night work limits where applicable, and rest entitlements. There is no requirement to keep a minute-by-minute log, but records must be sufficient to show that statutory limits are being respected in practice. Where on-call time may count as working time, this obligation extends to recording those periods accurately.

In practice, many employers track only scheduled shifts and actual call-outs, ignoring the wider on-call window. This creates a structural weakness. If a regulator or tribunal later determines that the on-call period itself constitutes working time, the employer will have no contemporaneous evidence to demonstrate compliance with the 48-hour weekly average or rest requirements. In these circumstances, the absence of records can itself amount to a breach, even if working time limits were not exceeded in reality.

Pay compliance creates an additional layer of record-keeping risk. Employers must retain sufficient payroll and time records to demonstrate National Minimum Wage compliance for each pay reference period. Where on-call availability time is arguably payable, employers must be able to show how hours were calculated and how pay rates were applied across each period. Flat allowances without supporting hour calculations are a common point of failure.

From a systems perspective, regulators increasingly expect on-call work to be visible within workforce management tools, not managed informally by managers or workers themselves. Spreadsheet tracking, manual logs or retrospective reconstruction of hours are treated with scepticism, particularly where fatigue or underpayment issues are alleged.

Section E summary

Employers must be able to evidence how on-call hours, rest and pay are managed. Failure to keep adequate records can itself constitute a breach and significantly undermines the employer’s ability to defend enforcement action or tribunal claims.

Section F: Can employees opt out of working time limits for on-call work?

The 48-hour weekly working time limit is often treated by employers as the primary compliance control for on-call arrangements. While opt-outs can provide flexibility, their scope is frequently misunderstood, leading to a false sense of security.

Under the Working Time Regulations 1998, individual workers may agree in writing to opt out of the 48-hour average weekly limit. Where a valid opt-out is in place, on-call hours that count as working time can lawfully push total weekly hours above the statutory maximum. However, this flexibility is narrower than many employers assume.

First, the opt-out applies only to the 48-hour weekly average. It does not remove or dilute any other working time protections. Daily rest, weekly rest and night work limits remain fully enforceable. Employers who treat opt-outs as a blanket waiver of working time obligations expose themselves to immediate non-compliance if on-call call-outs interrupt rest without compensatory rest being provided.

Second, opt-outs must be genuinely voluntary. They cannot be imposed as a condition of employment, either explicitly or through indirect pressure. In on-call-heavy roles, tribunals will scrutinise whether workers had a real choice or whether opting out was effectively required to remain employed or progress.

Third, opt-out agreements must be capable of being withdrawn on notice. Workers retain the statutory right to cancel an opt-out, typically on up to three months’ notice, and employers must be able to accommodate this without detriment.

Finally, opt-outs do not remove the need for risk management. Employers remain under a duty to protect worker health and safety. Excessive hours driven by on-call demands, even where an opt-out exists, can still trigger regulatory intervention if fatigue risk is not properly assessed and controlled. Opt-outs also have no effect on National Minimum Wage obligations.

Section F summary

Opt-outs provide limited flexibility but do not override rest rights, pay obligations or health and safety duties. They must be voluntary, withdrawable and supported by active fatigue management to avoid compliance failure.

Section G: Common on-call compliance mistakes employers make

Most on-call compliance failures arise from predictable patterns rather than novel legal issues. Employers often repeat the same structural mistakes across different sectors, leaving themselves exposed despite acting in good faith.

One of the most common errors is assuming that on-call time only counts as working time when a worker is actively responding to a call. This overlooks the legal test around restriction and availability. Where response times are tight or movement is constrained, the entire on-call period may qualify as working time, regardless of how quiet the shift appears in practice.

Another frequent mistake is relying on outdated assumptions around sleep-in shifts. Some employers continue to operate on the basis that sleep-in time is categorically unpaid or excluded from working time. This position no longer reflects the current legal landscape. Where workers are required to remain at a specified location and respond if needed, the risk of misclassification is significant.

Employers also commonly fail to assess cumulative fatigue. On-call work is often layered onto standard shift patterns without any holistic review of total hours, rest disruption or recovery time. Even where individual shifts appear compliant, the combined effect of repeated on-call duties can create sustained working time breaches and health and safety exposure.

Poor contractual drafting compounds these issues. Vague on-call clauses that grant wide discretion to managers, impose undefined response times or fail to address rest and pay consequences leave employers with little protection when arrangements are challenged. Tribunals and regulators place limited weight on contracts that do not reflect how on-call work actually operates.

Finally, many employers underestimate the enforcement risk. On-call issues frequently come to light through unrelated triggers, such as grievances, accidents, whistleblowing disclosures or HMRC minimum wage audits. By the time scrutiny begins, it is often too late to retrofit compliant systems.

Section G summary

On-call compliance failures are usually systemic rather than accidental. Misunderstanding restriction levels, relying on outdated assumptions and ignoring cumulative fatigue are the most common ways employers create avoidable legal exposure.

Section H: How should employers design compliant on-call arrangements?

Designing lawful on-call arrangements requires deliberate choices rather than inherited practices. The central compliance objective is to ensure that on-call systems align with how UK law assesses control, restriction, rest and pay, while remaining operationally workable for the business.

The first decision employers must make is whether they are prepared to treat some or all on-call time as working time. Where operational needs require short response times, fixed locations or significant activity restrictions, attempting to categorise the arrangement as non-working time is rarely defensible. In these cases, employers are better served by explicitly recognising on-call periods as working time and designing rotas, pay structures and rest provisions accordingly. This approach reduces legal uncertainty and limits retrospective exposure.

Where employers wish to keep on-call time outside working time where possible, restriction levels must be carefully managed. Longer response windows, broader geographic freedom and minimal lifestyle restrictions all strengthen the argument that workers are not at the employer’s disposal during availability periods. These choices involve commercial trade-offs, but they directly influence legal risk.

Rest protection must be built into the system rather than left to informal management. Employers should pre-plan how compensatory rest will be provided following night call-outs or repeated disruptions. This may require delayed start times, protected recovery periods or alternative cover arrangements. From a compliance perspective, the absence of a documented rest strategy is a clear enforcement risk.

Pay structures should be aligned with legal risk rather than historic norms. Flat on-call allowances should be reviewed against actual hours and restriction levels to ensure National Minimum Wage compliance can be evidenced for each pay reference period. Where availability time is arguably payable, employers should model worst-case scenarios rather than relying on optimistic interpretations.

Employers must also be alert to operational drift. Changes in technology such as remote monitoring tools, automated alerts, mobile applications or GPS-based systems can materially increase restriction levels without any formal change to policy. What begins as a low-impact on-call arrangement can become legally restrictive over time if response expectations tighten.

Finally, governance matters. On-call arrangements should be documented clearly, monitored centrally and reviewed periodically. Employers who fail to revisit on-call systems often find that compliant designs quietly drift into non-compliance as workloads, technology and expectations evolve.

Section H summary

Compliant on-call arrangements are designed, not assumed. Employers must consciously balance restriction levels, rest protection, pay structures and technology impact, and review systems regularly to ensure they remain defensible under working time and pay law.

FAQs

Is on-call time always treated as working time in the UK?
No. On-call time is only treated as working time where the worker is required to be at the employer’s disposal. This will always be the case where the worker must remain at the workplace and may also apply where on-call arrangements away from the workplace impose significant restrictions on movement, response time or personal activities.

Does on-call work count towards the 48-hour weekly limit?
Yes, where on-call time qualifies as working time, it must be included in the calculation of the average 48-hour weekly limit over the applicable reference period. Employers who exclude qualifying on-call hours risk breaching the Working Time Regulations 1998 even if actual call-outs are infrequent.

Do employees have to be paid for on-call time?
Potentially. If on-call time places the worker at the employer’s disposal, it is likely to count as payable time for National Minimum Wage purposes. Availability arrangements with minimal restriction may only require payment for actual call-out time, but this depends on the facts of the arrangement and must be assessed pay reference period by pay reference period.

Can rest rights be waived for on-call work?
No. Daily and weekly rest rights cannot be opted out of. Where on-call work interrupts rest, employers must provide equivalent compensatory rest as soon as possible. Failure to do so creates both working time and health and safety risk.

Does a 48-hour opt-out remove all on-call working time risk?
No. A valid opt-out only removes the 48-hour weekly average limit. It does not affect rest rights, night work limits, pay obligations or health and safety duties. Employers who rely on opt-outs as a complete solution often remain non-compliant.

Who enforces on-call working time breaches?
The Health and Safety Executive enforces working time limits and rest requirements, while HMRC enforces National Minimum Wage compliance. Tribunal claims may also arise through unlawful deduction from wages, whistleblowing or detriment claims linked to fatigue or workload.

Conclusion

On-call work is one of the most compliance-sensitive areas of UK employment law because it rarely engages a single obligation in isolation. Decisions about how on-call time is classified ripple across working time limits, rest entitlements, pay compliance and health and safety duties. Where employers get the classification wrong, exposure tends to accumulate quietly and surface only when enforcement or dispute action is already underway.

The consistent legal theme is control. The more an on-call arrangement restricts a worker’s freedom, the more likely it is that the time will be treated as working time and, in many cases, as payable time. Labels, allowances and informal practices do not alter this analysis. What matters is how the arrangement operates day to day and whether the employer can evidence compliance across hours, rest and pay.

For employers, defensible on-call arrangements require conscious design choices rather than inherited assumptions. This means deciding upfront whether restriction levels justify treating on-call time as working time, embedding compensatory rest into rotas, aligning pay structures with legal risk and maintaining reliable records. Opt-outs may offer limited flexibility, but they do not remove core obligations or health and safety accountability.

Handled properly, on-call work can be managed lawfully and commercially. Handled casually, it remains a frequent trigger for regulatory scrutiny, back-pay liability and reputational damage.

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