The New Jersery resident state income tax return does require taxpayers to include a municipality code. That code does not affect the computation of the tax at all, however. Instead, the instructions simply state that these "codes are for Division of Taxation purposes only". I did not dig much deeper than that to figure out why it is required, though my best guess is similar to ShyCat's; it is likely information gathered by the state to allocate some state funding to the municipalities or for use tax purposes. Why the software you used required it for computation of income tax I have no idea. That may just be an over abundance of caution given how the program was designed.