Retrospective notification effect: treated as effective from commencement, with a bar on refunds for collected UT tax. The notification identifying the administering authority for GST supplies is deemed to have retrospective effect from the commencement of the GST law, fixing legal character and tax liability as if the notification had existed from the start; additionally, a bar prevents refunds of Union territory tax collected that would not have been collected had the notification been in force at all material times.