Hi there, many thanks for your patience. If your nominated working days or days off are not stipulated in the contract, and it was never communicated that you have a permanent set of working days, they can potentially vary these. Your only argument on challenging this would be to try and show that it has become an implied contractual term.
There is a principle in law known as ‘custom and practice’, under which certain terms may become implied into an employment contract. This makes them contractually binding even if they are not written down anywhere. This area of law is rather complex and it is usually only down to the tribunals to establish with certainty if something had become an implied term. Nevertheless, it does not prevent employees from directly raising this argument with their employers in any negotiations.
From a legal perspective, to become an implied term a practice must be "reasonable, notorious and certain". In simpler terms this means it must be well established over a period of time, known to employees and clear and unambiguous. So it would need to have been clearly communicated to staff so that they have a degree of expectation for it and then it must have been consistently applied for a substantial period of time. Therefore, something that is uncertain, not widely communicated or applied consistently or has just been around for a few months is unlikely to qualify.
Case law has suggested that the following are important factors when considering whether a term has become implied into a contract:
· On how many occasions, and over how long a period, the terms in question have been applied - the more times they have been applied and the longer the period over which this has occurred, the stronger the argument they had become implied into the contract
· Whether the terms are always the same - large differences will make the argument they had become implied weaker
Whilst the argument of custom and practice can be raised with the employer in negotiations, they could of course refuse to accept it and if that is the case it can only realistically be challenged by taking this to an employment tribunal. Before that option is pursued it may also be worth raising a formal grievance to give the employer one last chance to resolve this internally.
So it does mean that you can raise this as an argument but if the employer does not take it into account and still proceeds with the changes, you may have to eventually resign and claim constructive dismissal as you cannot force them to keep the current arrangement.
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