A charity I am working with has asked about the legal and tax implications of providing its volunteers with an honorarium payment of £1000 (or a gift voucher) at the end of the year (just before Christmas). It wants to give this only to volunteers who have attended 75% of the meetings they are encouraged to attend (approx 4/6). It's a voluntary honorarium - i.e. volunteers don't have to accept it - and some have said they don't want it, others have expressed concern about the impact on their benefits / tax. 

The honorarium is only for volunteers who have committed a certain amount of time - does this make it a greyer area? 

What is the line on when this becomes payment rather than a gift, and therefore should be set at minimum wage. And, if it is payment, then is the volunteer actually an employee and entitled to employment rights? 

Does it make a difference if it's cash paid or a voucher given?