The list of allowable adjustments to basis is in publication 523. You may want to review it to make sure you did not miss any adjustments.
https://www.irs.gov/forms-pubs/about-publication-523
If this occurred in 2023, you need to make estimated tax payments to avoid an underpayment penalty. Pay at least 2/4th of the extra tax you expect to owe right away, 1/4 before September 15, and 1/4 before January 15, 2024.
