Please read this:
https://ttlc.intuit.com/questions/3373202-third-party-sick-pay-being-taxed-by-nj-state-this-year-was...
Your employer must prepare and sign this form, which you will then mail to NJ with your tax return:
http://nj.gov/treasury/taxation/pdf/other_forms/tgi-ee/2002/022440.pdf
