@zxiong89 --
Actually, your employer was correct not to withhold NY taxes when you were a non-resident of New York.
Here is what the New York Appellate court ruled:
"A nonresident who works in another State but who performs no work in New York is not subject to New York State tax liability no matter for whose convenience or necessity he performs the work."
https://casetext.com/case/hayes-v-state-tax-comm
If you never physically worked in NY, not even for a single day, during the time that you were not a resident of NY, then your work income from that period of time is not taxable by NY.
New York's "convenience of the employer" rule applies only to non-resident taxpayers who work both within and without New York State during the tax year.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
