Compulsory service charges should be treated just like PAYE wages if paid to the employee.
If card and cash tips are pooled together and distributed by a troncmaster, it is the troncmaster who is responsible for making sure Income Tax is paid on the tips. If the employer pools and distributes the card tips or voluntary service charges among the team, it is the employer who should make sure Income Tax – and in this case, National Insurance too – is paid through PAYE.
If you have a troncmaster, it is the business’ responsibility to tell HMRC that there’s a tronc and who the troncmaster is.
Your staff is responsible for paying tax (no National Insurance, in this case) on their own cash tips received directly from customers. Because the tip change is officially the employee’s property, the business should not get involved in that, although it is good to offer guidance on how to declare the tax.