The European Court of Justice has recently reaffirmed, in the case of in Sobczyszyn v Skola Podstawowa w Rzeplinie, that where a worker is unable to take their annual leave before the end of the holiday year due to sickness they will be entitled to carry it over to the following holiday year.
Workers will, therefore, continue to accrue holiday entitlements during sick leave and be permitted to rearrange any pre planned holiday where it coincides with any sickness. It makes no difference whether the leave has been scheduled or booked - if sickness prevents the worker from taking annual leave he or she must be allowed to take holiday at a later date following recovery.
This decision comes as no surprise, but once again highlights the conflict between UK law (Working Time Regulations which state that annual leave can only be taken in the year to which it relates) and European law/ECJ’s views on the European Working Time Directive. Given the current political climate and the impending Brexit negotiations, such conflict is unlikely to be addressed by the UK government anytime soon. That said, ECJ’s rulings all have legal force in the UK until the Brexit negotiations are complete and therefore, employers must still remain compliant with EU laws in the interim 
and thus ensure employees are able to carry forward paid annual leave where sickness has prevented that worker from taking such leave.