It is good practice only to reimburse their out of pocket expenses, and buy them lunch etc if their volunteering hours necessitate this. Extensive guidance can be found on the Volunteering England website.
It is important to obtain receipts for all expenditure which they have incurred (except car / van mileage, which can be reimbursed at 45p per mile for the first 10,000 miles. See the HMRC guidance on this).
The risk is that you may be perceived as paying the individual and this may be a tax or benefit issue.
It is a good idea for the organisation to have a policy on payment of volunteers’ expenses. WYCAS have a Good Practice Guide on this subject.
Posted in: Procedures & Controls