In simple terms, All companys must pay tax, this is even if the company does not hav taxable profits....This tax is called MAT
Minimum Alternate Tax provides that where the total taxable income of a company is less than 30 percent of its book profits, computed in accordance with the Companies Act, 1956, the company would be required to pay income tax on 10.5 percent of its book profits.
A small amendment to what Ms.Annie said. Not all companies are required to pay tax. All companies who exhibit book profit must pay tax, not withstanding their taxable income as computed under IT Act is zero!