Registration validity and advance tax deposit requirement for casual and non-resident taxable persons ensures prior deposit before supplies. The certificate of registration for a casual or non-resident taxable person is valid for the period applied for or ninety days from the effective date, with possible extension for a further period not exceeding ninety days. Such persons must make an advance deposit of tax equal to their estimated liability for the registration period, and any additional deposit for an approved extension. Deposits are credited to the electronic cash ledger and utilised under the prescribed utilisation mechanism.