To amend the Internal Revenue Code of 1986 to modify the earned income tax credit to account for the amount by which economic growth has outpaced income growth, and for other purposes.

Grow American Incomes Now Act of 2017 or the GAIN Act This bill amends the Internal Revenue Code, with respect to the earned income tax credit (EITC), to: (1) increase specified credit and phaseout percentages, (2) increase the earned income amounts and the phaseout amounts, (3) decrease from 25 to 21 the minimum eligibility age for individuals without qualifying children, and (4) allow employees to elect to receive advance payments of the EITC from employers when wages are paid.