Update W-4 tax withholding settings

Clients can update a worker's W-4 tax withholding settings. These are the elections made on a federal Form W-4, and they affect the calculation and withholding of federal income tax. Changing a worker’s W-4 tax withholding settings requires specifying an “effective date” for the change. This is the date, in the worker's local time zone, the change becomes effective.