@AliciaP1 Thank you! I actually edited my question a few minutes after I sent it, but I can see that you didn't receive the update.
Here's my edited question (I realized after I first posted that the circular issue wasn't my initial question with Col B):
"Point is, I'm trying to figure out what the formula for Col B is ... I do not know what " any loss or deduction items disallowed due to basis limitations in prior years" means. I DO have my total losses/deductions carried forward each year... but how do I know if they were disallowed? (as in what is the definition of "disallowed" in this very specific context)?) Thank you!"
