The Government Grant is a feature in Simburbia, added in the Optimisation Update. It replaced the Manual Audit and Build Token Return buttons. The opposite of the Government Grant is the One Time Tax Levy, also added in that update.
The Government Grant is not available at the start of the game, it becomes available after a while of playing the game. You will be alerted when it is unlocked. In the Main Menu you can purchase a Government Grant for 100K. To use it, place it in the Plot Modification Selector and the Land Value of that plot will go up by 1. It can also be used on Power Plants or Parks, but since those don't have land value it will simply change the design of it. Government Grants have a max of 4 uses.