When attempting to determine a taxpayer's residency status for the state of New Jersey, there are two important terms to know:
Domicile - The taxpayer's domicile is the place they consider their permanent home, the place where they intend to return after a period of absence (e.g., vacation, business assignment, educational leave).
While a taxpayer may live in multiple places, they only have one domicile. Their domicile does not change until they move to a new location with the intent to establish a permanent home there and to abandon their New Jersey domicile.
Moving to a new location, even for a long time, does not change their domicile if they intend to return to New Jersey. Their home, whether inside or outside New Jersey, is not permanent if they maintain it only for a temporary period to accomplish a particular purpose (e.g., temporary job assignment).
When assessing a taxpayer's domicile, the New Jersey Department of Taxation takes into account factors such as their stated intent, where they are registered to vote, their driver’s license and vehicle registration, family ties, the address on their federal tax return, where their bank accounts are located, and whether they participated in a New Jersey property tax relief program.
Principal Residence (Main Home) - The taxpayer's principal residence or main home is a home they own or rent and actually occupy as their permanent residence. It does not include a vacation home, a "second home", or property they own and rent to someone else.
Determining a taxpayer's residency status
Resident - A resident of New Jersey is an individual that either (a) is domiciled in New Jersey for the tax year or (b) maintains a permanent home in New Jersey and spends more than 183 days in the state.
Nonresident - A nonresident of New Jersey is an individual that either (a) is not domiciled in New Jersey and did not maintain a permanent home in New Jersey, (b) is not domiciled in New Jersey, maintained a permanent home in New Jersey, but did not spend more than 183 days in New Jersey, or (c) was domiciled in New Jersey, did not maintain a permanent home in New Jersey, and did not spend more than 30 days in New Jersey.
Part-Year Resident - A part-year resident is an individual that moved into or out of New Jersey during the tax year.
New Jersey doesn't have a part-year resident form. At a minimum a part-year resident will file the resident Form NJ-1040 for the period of time that they were a resident of New Jersey. They will also need to file the nonresident Form NJ-1040NR if they received income from New Jersey sources while a nonresident.
What if one spouse is a resident and the other is not?
If a married couple are filing a joint federal return, and one spouse is a New Jersey resident and the other is not, the resident spouse can file their New Jersey tax return using filing status married filing separate return. Otherwise, the spouses can file a joint return, bearing in mind that all of their income will be taxed as if they are both residents.
To file separate returns, file the federal return and wait for the return to be accepted. Then, change the filing status for the primary taxpayer to married filing separately and complete the separate New Jersey return. If the spouse has a filing requirement with the state of New Jersey, a new federal separate return will need to be created for the spouse for the purpose of filing a separate New Jersey return.
Additional Information:
New Jersey State Tax Information
NJ DOT: Part-Year Residents and Nonresidents, Understanding Income Tax