I lived and worked in NY city for the first 8 months of the year then I moved to NJ for the last 4 months I work from home now in NJ for the same job which is based in NY all my taxes inc the last 4 months of the year were withheld in NY my W2 says NY on it how do I file

You must file tax returns for BOTH NY and NJ as part-year residents.

It will be a complicated return, as you must allocated income to each state.

Suggest you get professional tax help!

Also make sure your employer starts using your new NJ address - your W2 should reflect your residence.

Agreed!