Interesting service tax issues - 6

Here is an interesting service tax issue from a friend.

Mail me your views on it to mail id: ableindiaemail@yahoo.com

Dear Colleagues;

A hotel is receiving advance on booking of rooms. Rooms will be
occupied and thus service will be rendered at a later date.

My query is whether service tax is payable at the time of receiveing
of advance or when actual service is rendered.

If service tax is payable on advance then what happens if booking is
cancelled and

a) advance is refunded in full.
b) advance is refunded after cancellation of certain charges.

Kindly advise.

regards,