(m) "input service distributor" means an office of the manufacturer or producer of final products or provider or an outsourced manufacturing unit of output service, which receives invoices issued under rule 4A of the Service Tax Rules, 1994 towards purchases of input services and issues invoice, bill or, as the case may be, challan for the purposes of distributing the credit of service tax paid on the said services to such manufacturer or producer or provider, as the case may be;