@Angel Tr33We're glad to be of help.

No, you don't use NJ-COJ because there's no credit to be claimed.  Under the PA-NJ reciprocal agreement, taxes are payable solely to the resident state, which means the income is not being subject to double taxation.

What your client needs to do is to make sure he/she submits the exemption certificate to the PA employer ASAP, if not already done, to ensure NJ SIT will be withheld going forward.

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