Effective January 1, 2020, employers should be using the revised Form W-4 in the new hire process.
Click here to access the form from the IRS website. Employers may ask current employees to complete a new Form W-4 but the employer must advise the current employees that they are not required to furnish a new Form W-4 and that if the current employee does not furnish a new Form W-4, withholding will continue based on a valid form previously provided.
The IRS has published a list of frequently asked questions to assist employers in incorporating the new Form W-4 into the employment process.