When to start charging service tax ?

Hi All,

A client of mine is working as a freelancer and he has registered himself for service tax voluntarily. He was covered under export of services exemption earlier and hence was not liable to deposit any service tax, still he got himself voluntarily registered and filed NIL returns.

Now, he has started providing services to Indian clients as well from this year. My question is that should he start charging service tax from his clients right from the first invoice issued to an indian client for domestic services or should he wait till he crosses Rs. 10 Lacs taxable services (i.e. domestic services ) value and then start charging service tax ?

I am confused because I have read it a couple of times that if a person is voluntarily registered for service tax then he must start chargin and depositing service tax right from the first invoice.

Please help ... I could not find a solution to this query anywhere.

thanks