Form 8233 allows eligible visa holders to claim "exempt" from federal withholding on earnings as allowed by certain tax treaties. Eligibility is based on visa status and the substantial presence test. If eligible, you need to submit Form 8233 when you are hired or rehired, whenever you change job types or visa types, and each December for the upcoming calendar year if the tax treaty is to be applied. If an 8233 is not filed, the tax treaty will not be applied.