Example: Suppose you had an overall capital loss of $18,000 from stock trading in 2014. You were allowed to use $3,000 of the loss that year, and the remaining $15,000 carried over to 2015. You ended up with an overall gain of $20,000 that year. After applying the capital loss carryover, you are taxed on just $5,000 of capital gain.
You should have just $5,000 of capital gain in both the regular tax calculation and the AMT calculation. Your $15,000 capital loss carryover is available for both taxes. But your tax software may assume your AMT capital loss carryover is zero unless you explicitly plug the number into the AMT calculation.
https://fairmark.com/general-taxation/alternative-minimum-tax/amt-capital-loss-trap/
