On December 22, 2017, President Trump signed into law the Tax Cuts and Jobs Act (TCJA) that represents the most comprehensive changes to the tax law in over 30 years. TCJA impacts all taxpayers by eliminating or changing many long-standing rules and adding new provisions. While Congress made most corporate changes permanent, the changes to the individual rates and deductions are temporary to comply with budget rules under reconciliation. As a result, most individual changes are effective for tax years beginning after December 31, 2017 and before January 1, 2026; effectively suspending existing law with the 2017 rules reinstated in 2026. This supplement updates the text for these revisions as well as other important changes since publication. Changes made retroactively affecting 2017 tax returns are discussed first; then changes affecting future years are highlighted in the next section of this supplement. These changes are keyed to the 2018 edition by chapter and section number. RETROACTIVE CHANGES Chapter Section Brief Description of Change 5 5.4.1 5.7.2 The minimum amount of unreimbursed medical expenses that are not deductible is reduced from 10% to 7.5% of AGI for 2017 and 2018 for all taxpayers (regardless of age) for regular income tax and for the alternative minimum tax (AMT). The 10% threshold is reinstated in 2019 for regular tax and AMT. 5 & 9 5.4.5 9.3.1 The $100 floor for casualty losses from disasters in 2016 or 2017 is raised to $500 per casualty and the 10%-of-AGI threshold does not apply. Taxpayers who do not itemize can increase their standard deduction by the net disaster loss for these two years. 7 7.3.2 Bonus Depreciation is increased from 50 percent to 100 percent for purchases after September 27, 2017. A more detailed discussion of this provision with an example follows. Retroactive Change to Bonus Depreciation Prior to the passage of the Tax Cuts and Jobs Act, bonus depreciation only applied to new (not used) property at a 50% rate. TCJA temporarily increased bonus depreciation to 100% for assets acquired after September 27, 2017 and extended it to used property. The 100% rate will begin to phase out after 2022 and expire at the end of 2026.