Advance payment of interest-tax requires scheduled instalments and triggers interest and reassessment-linked charges for defaults and shortfalls. Substituted provisions require advance payment of interest-tax in three instalments during the financial year and treat end-of-year payments as advance payments. Late or non-furnished returns attract simple monthly interest on the determined interest-tax reduced by advance payments, with rates specified and application rules for reassessments, demand notices, and refunds. Failures or shortfalls in advance payments incur interest from the next financial year until assessment, with calculation adjustments when tax is paid or reassessed. A deferment rule applies a lower short-term monthly interest on instalment shortfalls. Concealment of chargeable interest attracts a penalty up to a prescribed multiple of the tax sought to be evaded.