How long can an employee be expected to "act up" to a more senior position before the arrangement will be regarded as a permanent promotion?
Whether or not an arrangement for an employee to "act up" to a more senior position will become a permanent promotion depends on what has been agreed between the parties.
If the employee has agreed to "act up" on an open-ended basis, but there is no written agreement in place, there is a risk that the arrangement could become permanent through custom and practice. As the employee's job title and salary are express terms of the contract, it is difficult for custom and practice to supersede them, particularly where it is made clear to the employee at the outset that it is a temporary role. However, where an employee assumes the job title, duties, responsibility and salary of the new role and there is no periodic review of the arrangement, it is possible that the role could become permanent as more time passes.
If there is a written agreement in place, specifying the time frame over which the employee will "act up", and what the terms governing the arrangement are, there is little risk that the arrangement will become permanent. Where a time frame has not been specified, but it is set out clearly in writing that it is a temporary arrangement and there are periodic reviews in discussion with the employee, again it is unlikely that it will be deemed to be a permanent promotion.
It is therefore good practice for employers to have a written agreement setting out the arrangement from the outset to avoid the potential risk of the arrangement becoming a permanent promotion.