Tally.ERP license is perpetual. That is one-off. However, there is a secondary license that offers some services to Tally Users on optional basis.
Hotline: +234 (0) 810 509 0001
TSS (formally known as: Tally.NET) is an optional license that keep your Tally.ERP9 or Tally Prime up-to-date. It also gives access to features like Remote Access, Data Synchronisation, Web Reports and Product Upgrades. TSS means Tally Software Service