The rate of tax depends on the nature of contract. For ex. Construction etc. of canal, dams for government, governmental authority or railways related projects are eligible for beneficial rate of 12%. Further, were major work is earthwork etc. then even 5% rate is available and all other contracts and other than govt contracts, the rate of tax is 18%. For detailed list, you can refer notification. no. 11/ 2017 and 20/2017 rate