FILE - This Aug. 19, 2015, file photo, shows the Internal Revenue Service Building in Washington. The tax overhaul bill has yet to be passed at this point. But if it does, those changes will take effect in 2018. The IRS said that it is closely monitoring the bill and expects to issue initial withholding guidance in January, which would allow taxpayers to begin seeing the benefits of the change as early as February. (AP Photo/Andrew Harnik, File)