I ask my question in form of below illustration.
A:- Service Receiver
B:-Service Provider
B provide service of commission. It charge and collect the amount from A since last 4 years
All of sudden B know that it is liable for service tax so it paid service tax on receipt of all last 4 year commission.
B send the challans to A to reimburse service tax paid by B of last 4 years.
Whether A can claim it as expenses or input service tax credit ??