The simple answer to that is no. Employees have a right to request annual leave but you do not have to agree to the request. If an employee becomes sick during a period of annual leave (s)he has the right to have it converted to sickness rather than holiday but there is no right to change this the other way.

Many employers will refuse to allow employees to treat sickness as holiday for a variety of reasons. It masks the frequency of sickness absence, it can result in people qualifying for bonuses that they shouldn’t receive and it goes against the purpose of annual leave, which is a rest from work.

Your employee will continue to accrue his entitlement to annual leave while he is on sick and if he is unable to take it during the leave year due to ill health then you will have to allow him to carry it over into the next year. You need to consider the nature of the sickness and how long it is likely to continue for.

While you have no obligation to agree this request, and it would be inadvisable to apply it retrospectively to time already taken off on grounds of sickness, you can choose to agree a request for leave for a period of time in the future. This would help alleviate the financial pressure on your employee and means that you aren’t faced with a potentially large amount of leave to fit in on your employee’s return.

See also: Leave IT to the experts