If my "Fair Market Value per Share on Exercise Date" (Box 4) is lower than "Exercise Price per Share" (Box 3) on Form 3921, what should I enter for my "ISO Adjustment"?

[TomYoung · Accepted solution]

You don't have one.  The "spread" between exercise price and FMV only works in the "positive" direction.  You have stock that, apparently, is worth less than you paid for it.  So you basis per share is what you paid for it.  You have no adjustment.

Tom Young