Hello I am a solicitor with over 15 years experience. I will try to help you with this. You can include a service charge but the industry standard for this is to make it voluntary. If you make it compulsory then a customer could still refuse to pay it if they felt that inadequate service had been provided. There is no rule preventing you from including a service charge in your bills.
is this practice legal of charging service charge, i had a customer last night who said hr found out that he does not have to pay service charge if he doesnt want too, so he refuse to pay service charge, and so did other few customers, so what do i do in this situations