There is nothing specific in law which states that TOIL is treated as salary sacrifice and cannot be allowed to operate. Whilst not as common as it used to be, TOIL is still used by some employers and it is legal. You are correct that no specific laws deal with it hence why it is usually something which is agreed between the employer through a specific agreement, or through custom and practice.
If there is nothing specific in writing in your case then it is most likely going to be 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
· The extent to which the terms are publicised generally - there must be widespread knowledge and understanding amongst the workforce that such terms were being applied
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.
I trust this has answered your query. Please take a second to leave a positive rating by selecting 3, 4 or 5 stars above - this is an important part of our process and recognises the time I have spent assisting you. If you still need me to clarify anything else, please reply on here and I will assist as best as I can. Thank you