Procedure to collect service tax

Hello Everyone!

i run a commercial coaching center and it is a sole propritor ship firm.

till now we have not collected any service tax and did not pay any service tax to govt. I have also not done my IT returns till now. i do not have Service tax registration number but I have a pan?

now one of my client wants to pay service tax. can i collect service tax witout ST registration? If so what should be mentioned on the invoice if not what steps can i take now to collect the same.

if possible provide me the formt

thanks