On page 3 of the Instructions for Form 8615, the Schedule D Tax Worksheet modification to figure the line 7 tax has been revised to account for the addition of Line 18b in the Schedule D Tax Worksheet, located in the 2018 Instructions for Schedule D, which were revised on May 15, 2019. The original tax calculation did not work correctly with the new TCJA regular tax rates and brackets for certain taxpayers who had 28% rate gain (taxed at a maximum rate of 28%) or unrecaptured section 1250 gain (taxed at a maximum rate of 25%). We corrected and updated the Instructions for Form 8615 by adding a reference to the new Line 18b for the Schedule D Tax Worksheet with a modified calculation for Form 8615 filers.
The corrected language is in the updated Instructions for Form 8615 at the link above. If you downloaded the Instructions for Form 8615 before May 17, 2019, you should download it again. You should use the updated instructions to figure your tax. For more information, see the Recent Developments article posted at www.irs.gov/ScheduleD.