Sir,
Para 2.2 of CBE and C Circular No. 97/8/2007-ST dated 23.8.2007 states-
"Any person liable to pay service tax, who,-
(a) provides taxable service from more than one premises;
(b) receives taxable services in more than one premises; or
(c) has more than one premises engaged in relation to such taxable service, may seek centralised registration, provided he does centralised billing or maintains centralised accounting in respect of such taxable services in a premises. In certain cases the centralization can be at the zonal/regional level. In such case, each of such offices is to be registered individually. Such registrations are to be granted by the jurisdictional Commissioner where such offices/establishments are located.
Therefore you have give your head office/centralised Office when the billing system and accounting system are maintained as registered premises and this premises will be treated as registered premises. You have to enclose in an annexure with ST-1 Form (Application for Registration) the addresses of other premises from where also you are providing the services. In the case of centralised registration Commissioner of Servidce Tax/Central Excise will be the authority to issue the registration certificate.