At the close of February, the IRS released an updated tax withholding calculator on IRS.gov and issued a new Form W-4, Employee's Withholding Allowance Certificate. Employees can use the online calculator to check their 2018 tax withholding following passage of the Tax Cuts and Jobs Act in December. If employees choose to adjust their withholding, they can now complete and submit the revised Form W-4 to their employer.
The IRS also posted new Withholding Calculator Frequently Asked Questions.
Read more at: SHRM Article - IRS Issues New Form W-4