Advance tax computation: estimate or prior assessed income determines liability, reduced by tax collectible or deductible at source. Advance tax is computed either from the assessee's estimate of current income or, where the Assessing Officer acts, from the higher of the latest regularly assessed total income or a later returned total income; income-tax is calculated at current-year rates and reduced by tax deductible or collectible at source on income included in the computation, except where deduction or collection was not made by the person responsible. Inclusion of net agricultural income and special rates for certain Hindu Undivided Families apply when the Finance Act so prescribes.