Service tax exemption for construction of airport or port: relief for pre-existing contracts certified by ministries. Temporary service tax exemption covers construction, erection, commissioning or installation of original works for airports or ports under contracts entered into before the cut-off and with applicable stamp duty paid; exemption conditioned on certification by the relevant central ministry. Refunds are payable for tax collected that would have been exempt, subject to a six-month filing period measured from the enactment milestone in the amending finance legislation.