Answer
Nitrogen forms 3 bonds to have a formal charge of 0. But Nitrogen has 4 bonds so the formal is +1. Chlorine has 8 electrons so its formal charge is -1. The overall charge is 0 because the positive charge of $NH_{4}$ and the negative charge of chlorine get canceled.
Work Step by Step
Formal Charge (FC) = [number of valence electrons] - [number of non-bonding electrons] - 12 [shared electrons]
FC (nitrogen) = 5-0-4 = +1
FC (chlorine) = 7-8-0 = -1
FC (hydrogen) = 1-0-1 = 0
