IRS Reduces Certain 2018 Tax-Related Limits: Revenue Procedure 2018-18 modifies and supersedes certain sections of Revenue Procedure 2017-58 to reflect amendments to the Code under P.L. 115-97. Revenue Procedure 2017-58 provided the 2018 cost-of-living adjustments for inflation for certain items, including the tax tables. The changes made by Revenue Procedure 2018-18 are retroactive to January 1.