@BillM223 customer did not say it was a NY company, it appears it was a TX company, unless there are additional facts not stated.
@as10bs if you perform services for your employer while living in NYC, that is NY state and NYC source income, even if the employer is headquartered out of state.
https://www.tax.ny.gov/pit/file/nonresidents.htm
You owe New York and New York City a non-resident tax return that reports and pays income tax on your New York source income -- that is, income you earned while living in New York City for those 150 days. Income that was paid before you moved to NYC or after you left (such as your bonus, apparently) is not NY source income.
The instructions for form IT-203 require you to allocate your total federal income to NY sources. You should be able to simply list all your income you earned while living in NY, from your paystubs based on when you worked and were paid. The worksheet on page 18 of the instructions does not require you to divide the total income by the number of days. Where did you get that calculation?
https://www.tax.ny.gov/pdf/current_forms/it/it203i.pdf
