IRS Releases 2018 Withholding Tables
The IRS has released the 2018 withholding tables (IRS Notice 1036). The tables should be used as soon as possible, but not starting later than February 15, 2018. Until implemented, the IRS recommends continuing to use 2017 tables.
As for the Federal supplemental withholding rate, often used for taxable relocation reimbursements, the rate was lowered from 25% in 2017 to 22% in 2018. For supplemental income exceeding $1,000,000, the rate was also lowered from 39.6% to 37%.