Chartered Accountant
60 Points
Joined February 2008
Kindly refer 25/2012 MEGA EXEMPTION NOTIFICATION as amended by Not 3/2013 para 29. If it is an intermidiary process during manufacture which falls in the said para 29 then no service tax would be applicable.
However it is simple repair of a goods then liable to service tax.
Since you are a service provider then you should raise Invoice. Debit note is issued when any kind of accounting adjustment is done after billing related to sold goods or service is rendered.