Voluntary Overtime Pay Rules


Voluntary overtime can offer an effective way to resource surges in work or to address staffing issues. However, employers must ensure they are managing overtime correctly, including giving employees their full entitlements to overtime pay.

In this guide for employers, we look at the rules relating to voluntary overtime pay, including how voluntary overtime differs to compulsory overtime, who is entitled to be paid for voluntarily working additional hours and the impact of voluntary overtime on holiday entitlement.


What is voluntary overtime pay?

Voluntary overtime is typically defined as any hours worked by an employee, on an agreed or voluntary basis, in addition to their normal fixed or contractual working hours. Voluntary overtime pay is therefor the rate of pay, enhanced or otherwise, for undertaking these additional hours.


Voluntary overtime rules

There may be various reasons as to why an employee is asked to work overtime, for example, due to sickness-related staff shortages or to enable an employer to cope with an increase in customer demand.

Overtime can be either voluntary or compulsory. The requirement for an employee to work additional hours over and above their normal fixed or contractual working hours will depend on their employment contract terms.

Voluntary overtime is where there is no contractual obligation on an employer to offer additional hours, nor is there any obligation on the employee to work these hours if offered. In other words, there is nothing in the contract of employment obligating the employee to work extra hours beyond their contracted working hours.

Further, in circumstances where overtime is voluntary, an employee should not be subject to any detriment for refusing to work any more hours than they are contractually required to do.


Compulsory overtime rules

There are two types of compulsory overtime, namely guaranteed and non-guaranteed. Guaranteed compulsory overtime is overtime that an employer is contractually obliged to offer and, equally, an employee is obliged to accept.

This could be, for example, where employees are scheduled to work overtime on the last Friday of every month to fulfil a regular order for a particular customer over a certain period.

Non-guaranteed compulsory overtime, on the other hand, is where the employer is not obliged to offer the employee any additional hours although, where it is offered, the employee is contractually bound to undertake this extra work.

By way of example, this could be where an employer anticipates the need for employees to work extra hours during busier times of the year, but doesn’t know exactly how much overtime will be required in advance.


Maximum working hours rules

As an employer, it is important to remember that all working hours, including overtime, are governed by the Working Time Regulations 1998. The regulations limit the number of hours that employees can work each week, albeit on an average basis.

By law an employee cannot work more than 48 hours a week on average, unless they decide to work more by opting out of the 48-hour weekly limit or, alternatively, they do a job not covered by the regulations on working hours.

In broad terms, “working hours” will include any time that an employee is at the employer’s disposal, in other words, doing things they have been asked to do for the purposes of their job. This can include, for example, job-related training, any travel time between client or customer appointments or even working lunches.

Working time can also include paid overtime, as well as unpaid overtime that the employee has been asked to do and the employee has agreed to. It does not, however, include unpaid overtime that the employee has simply volunteered for, such as staying late to finish something off or to help out once in a while.

When calculating an employee’s working hours for the purposes of the regulations, these are normally averaged out over a period of 17 weeks. Unless the employee has opted out of the 48-hour week, these must not exceed an average of 48 hours weekly over this period.

As such, an employer can ask an employee to work more than 48 hours in a single week, and an employee can agree to do so, as long as the employee’s hours are reduced within the relevant timeframe so as to even out their average weekly hours.

To opt-out of the 48-hour time limit, this must be done voluntarily by the employee and in writing. Further, an employee who is asked to opt-out must not be sacked or treated unfairly for refusing to do so. However, certain workers are not permitted to opt-out by law, for example, those in charge of operating vehicles or those under the age of 18.


Who is entitled to voluntary overtime pay?

In practice, the use of paid overtime is more common with hourly paid employees than salaried staff, although salaried employees can still receive overtime pay. However, in either case, there is no automatic right to receive any additional payment or to be paid at a higher rate for any voluntary overtime worked. In other words, there is no minimum statutory level of overtime pay.

Whether or not an employee has a contractual right to voluntary overtime pay, and at what rate, will depend on what has been agreed between the parties, either verbally or in writing, for example, within an employment contract or staff handbook.

Where some form of contractual provision is made for overtime pay, it is open to an employer to offer a higher rate of pay than for normal working hours as an incentive for staff to work the additional time, although this is by no means mandatory.

By way of alternative to paid overtime, many employers offer time off in lieu to employees who are willing to work above their contracted hours. Time off in lieu means that any voluntary overtime hours worked can be taken off from work at a later date, in addition to any annual leave.

However, an employer must ensure that where an employee agrees to work additional hours on the basis that this time can be taken back at a later date, this does not take the employee below the national minimum wage for that particular pay reference period. In other words, the average pay for the total hours worked must not fall below the relevant minimum wage.


Part-time workers & voluntary overtime pay 

The voluntary overtime pay to which a part-time worker is entitled will not only depend on their individual contract of employment but also what contractual entitlements have been given to full-time employees.

In circumstances where a full-time employee is contractually entitled to an enhanced rate of pay for working overtime, part-time employees should usually receive the same rate of pay for additional hours worked by them. It is a legal requirement that part-time employees must not be treated less favourably than full-time workers.

However, unless the contract provides otherwise, there is no obligation on an employer to pay a part-time employee an overtime rate until they have worked the same amount of hours as their full-time counterpart or, alternatively, where they have worked during unsocial times, for example, late at night, and any full-time staff would get more pay in these circumstances.


Voluntary overtime pay & holiday entitlement 

By law, employees are entitled to a week’s pay for each week of statutory leave that they take. Almost all workers are legally entitled to 5.6 weeks’ paid holiday per annum. However, the question here is how this pay is calculated.

For an employee who always works fixed hours, without any overtime, the calculation should be straightforward. Their holiday pay entitlement will simply amount to their weekly normal remuneration.

In contrast, for employees whose working hours vary from week to week, the calculation becomes more complicated. This is calculated using an average of the total pay over the last 52 weeks worked for the full 5.6 weeks holiday entitlement.

In the case of East of England Ambulance Service NHS Trust v Flowers and others, in the context of a claim for unlawful deduction of wages, much-needed clarity was given by the Court of Appeal as to how overtime fits into this calculation.

In particular, it was held that overtime worked of the employee’s own volition is included when calculating statutory holiday pay entitlement, alongside any non-guaranteed and guaranteed overtime. It matters not that there is no contractual requirement to undertake overtime – rather, what matters is whether any pattern of work is regular enough to be considered part of an individual’s normal weekly remuneration.

As such, in circumstances where an employee works overtime that is sufficiently “regular and settled”, any calculation as to holiday pay entitlement must include voluntary overtime pay, up to the first four weeks of statutory annual leave entitlement. In contrast, where overtime is worked on an occasional and infrequent basis, in other words, where it is “exceptional and unforeseeable”, this does not need to be factored in when calculating holiday pay.

In summary, the Court of Appeal decision is not authority for the proposition that all voluntary overtime must now be included in the calculation of holiday pay, but rather each calculation must be approached on a case-by-case basis.


Overtime terms in employment contracts 

As set out above, whether or not an employee is required to work overtime, and on what basis, will depend on their contract of employment.

For the employer looking to rely upon either guaranteed or non-guaranteed compulsory overtime to provide for any anticipated business needs, this should be clearly set out within the written terms and conditions under which your employees are required to work.

Further, given the mandatory nature of this type of overtime, clear guidance should also be given as to the potential consequences for failing to work additional hours when required to do so. This can either form part of an individual’s contract of employment or be contained within the staff handbook.

In particular, in circumstances where an employee is contractually obliged to work overtime, on either a guaranteed or non-guaranteed basis, but they refuse to work any additional hours as required, this may be viewed as a breach of the contract for which the employee can be subject to disciplinary action.

In contrast, for the employer looking to deal with staff shortages or increased customer demand on a more ad hoc basis, a system of voluntary overtime may suffice. This can either be agreed in advance with your employees or as and when the need arises.

That said, it is again always best to set out in writing the basis upon which overtime will be worked, albeit voluntarily, including any enhanced rate of pay or time off in lieu. In particular, where you are asking employees to work additional hours in lieu of time off from work to be taken at a later date, you should also seek to agree the following detail:

  • When any accrued leave can be taken
  • The authorisation process for booking this leave
  • What if the contract ends before all accrued overtime is used and how the employee will be recompensed, if at all, for this unused time.

As an employer offering time off in lieu, you should always consider how much leave is allowed to accrue and how much time can be taken at once, as your business could be affected by when employees are looking to take this time back.

If you would prefer to deal with the amount and timing of any leave taken on an individual basis, you should ensure that employees are fully aware of this policy and only accept voluntary overtime having expressly agreed to this.

Further, regardless of whether the employee’s contract provides for either voluntary overtime pay or time off in lieu, you should keep an accurate and up-to-date record of how much overtime has been worked.

By having clear guidance as to how voluntary overtime will work, as well as a written record of what hours have been undertaken, this will help to minimise any disputes as to what is owed, either in terms of money or time, as well as how any holiday pay is to be calculated.


Need assistance?

DavidsonMorris are experienced advisers to employers and HR departments on all aspects of employment law and human resources, including drafting and reviewing contract terms and policies. With a clear overtime policy in place and implemented correctly, issues relating to voluntary overtime pay can be minimised and managed.

If you have a question or need advice on any aspect of employment contract terms, contact us.


Voluntary overtime pay FAQs

What is the difference between voluntary and compulsory overtime?

Compulsory overtime is when an employee is obliged to work overtime, typically due contractual terms, while voluntary overtime is when there is no obligation on the employee to work overtime or on the employer to offer overtime.

Does voluntary overtime count in calculating holiday pay?

Voluntary overtime that is sufficiently “regular and settled” should be included when calculating holiday pay up to the first four weeks of statutory leave entitlement.

Last updated: 20 May 2023


Founder and Managing Director Anne Morris is a fully qualified solicitor and trusted adviser to large corporates through to SMEs, providing strategic immigration and global mobility advice to support employers with UK operations to meet their workforce needs through corporate immigration.

She is a recognised by Legal 500 and Chambers as a legal expert and delivers Board-level advice on business migration and compliance risk management as well as overseeing the firm’s development of new client propositions and delivery of cost and time efficient processing of applications.

Anne is an active public speaker, immigration commentator, and immigration policy contributor and regularly hosts training sessions for employers and HR professionals

About DavidsonMorris

As employer solutions lawyers, DavidsonMorris offers a complete and cost-effective capability to meet employers’ needs across UK immigration and employment law, HR and global mobility.

Led by Anne Morris, one of the UK’s preeminent immigration lawyers, and with rankings in The Legal 500 and Chambers & Partners, we’re a multi-disciplinary team helping organisations to meet their people objectives, while reducing legal risk and nurturing workforce relations.

Legal Disclaimer

The matters contained in this article are intended to be for general information purposes only. This article does not constitute legal advice, nor is it a complete or authoritative statement of the law, and should not be treated as such. Whilst every effort is made to ensure that the information is correct at the time of writing, no warranty, express or implied, is given as to its accuracy and no liability is accepted for any error or omission. Before acting on any of the information contained herein, expert legal advice should be sought.

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