As soon as the IRS release the 2018 withholding tables.
The IRS usually releases next year’s federal withholding tables and various payroll publications (such as Publication 15 (Circular E), Employer's Tax Guide) in late November or early December. Due to the major changes in the “Tax Cuts and Jobs Act of 2017 “bill, the IRS has delayed releasing the 2018 withholding publications until January 2018.
In a statement, the IRS has indicated that new withholding tables will be published as early as January 2018. Once the IRS prepare and publish their guidance (Notice 1036) on withholding for 2018, Payroll Mate will be updated to include the latest payroll tax calculations. The IRS also noted that it will give employers and tax professionals sufficient time to test their payroll systems for the 2018 tax year.
Please always keep your Payroll Mate updated by selecting “Help > Check for Update” from the top menu inside the software.