As the IBOR transition continues, business teams have frequently heard from their tax departments and advisors that amending existing contracts to add IBOR replacement mechanics or replacing an IBOR rate with a new rate can have US tax consequences. The last major guidance from the Internal Revenue Service (the “IRS”) on this subject came on October 8, 2019 (back when taking a day to work from home might have been presumed to be a light day) in the form of proposed regulations under section 1001 of the Code (the “Proposed Regulations”). The Proposed Regulations were not without imperfection. On December 30, 2021, the IRS published final regulations for the IBOR transition (the “Final Regulations”). Most importantly, as discussed in more detail below, the final version no longer contains the requirement in the Proposed Regulations that the fair market value of the instrument after the replacement or addition is substantially equivalent to the fair market value of the instrument before the replacement or addition, replacing that standard with a list of modifications that fall outside the relief provided by the Final Regulations.