Hi Shittal,
If the value of taxable service provided in the previous year does not exceed 10 Lacs then the assesse is know as small service provider. The benefit of this is that service provider is not require to charge service tax on the taxable srvice provided in the following year upto a limit of 10 lacs.(Value of Service)
However the above scheme is optional.
As in your case he dint require to collect the service tax and he haven't done the same so there is no issue.
However he has paid the ST of his own and he can claim the same as refund as it was mistake of fact by him.
further, the above scheme shall have no imapct on the registration under service tax. So he need not worry for the same.
Regards
Ketan