Point of Taxation rules: service tax arises on spectrum assignment at the earlier of due date or payment, affecting valuation and credit. Point of Taxation for services by Government or local authorities for assignment of rights to use spectrum is the earlier of the date payment becomes due as per invoice/bill/challan or the date of payment; interest on deferred payments is includible in the value of the taxable service; CENVAT Credit for one-time assignment charges paid in a year may be availed evenly over three years, while credit for periodic charges is available in the year of payment, and credit may be taken on the basis of challans and specified documents even after the normal documentary period for government-assigned natural resource services.