Two different forms are at work in multi-state payroll and they are constantly confused. The state withholding certificate is the state analogue of the federal Form W-4; it sets allowances or exemptions for an employee who is subject to that state's tax. The nonresident exemption certificate is what an employee files to switch off withholding in a work state under a reciprocal agreement. Filing the wrong one leaves the obligation exactly where it was.
This is a determination aid, not advice.
StateSide encodes published state rules and applies them mechanically to the facts you enter. It does not know your
entity structure, your nexus history, your equity compensation, or the dozens of exceptions that turn a clean rule into
a judgement call. Every determination cites the state source it came from — verify against that source, and take
anything consequential to a payroll tax professional before you act on it.