IRS Developing Withholding Guidance for 2018 Tax Year: The IRS has announced that it is working to develop withholding guidance to implement the tax reform bill signed into law on December 22. The IRS anticipates issuing the guidance in January, and employers and payroll service providers will be encouraged to implement the changes in February. The guidance will be designed to work with existing IRS Forms W-4 that employees have already filed, and no further action by taxpayers is needed at this time.