As an investor in a pass-through entity you need to maintain and track your basis in this investment on an annual basis. As a result, you need to determine your basis "with certainty" and you should be able to do this. Your basis begins with your initial capital investment and gets updated annually for the applicable lines on your Schedule K-1.
See the attached link to provide some guidance:
https://www.irs.gov/pub/irs-pdf/p541.pdf?_ga=1.179735463.286459965.1455758446
Once you determine your basis, then you will know whether or not all the suspended losses can be deducted. If you have been allocated more losses than you have basis, then those losses cannot be deducted. This later result is a result of debt being used and then losses incurred.
Your basis needs to be positive in order to deduct any suspended losses.
Your AMT basis would be determined the same as noted above, except it will be adjusted annually for any AMT adjustments noted on your K-1 box 17.
You will need to have copies of all of your K-1's since the inception of the investment to accurately determine your regular and AMT basis. This may be somewhat easier for you if your K-1 box L has the tax basis box marked, but you will still have some work to do.
*A reminder that posts in a forum such as this do not constitute tax advice.
Also keep in mind the date of replies, as tax law changes.
