If they had a valuation done of the property when it was purchased showing the value of the timber you are in like Flint.  If not, you may have to show zero basis.

Someone else asked that question a few weeks ago and a practitioner who deals a lot with stumpage posted a great answer.  Unfortunately, the Search function here sucks, so you will never find it, unless it only appears on even days and you try again tomorrow.  

This one? https://proconnect.intuit.com/community/proseries-discussions/discussion/sale-of-cut-timber/00/62917

Schedule T did not make it into that conversation and I believe it should have.

https://www.irs.gov/instructions/it

No, the one I saw specifically mentioned stumpage, which made me think of Long John Silver.  

I think this is the one:

https://proconnect.intuit.com/community/proseries-discussions/discussion/re-stumpage/01/66744#M37354 

@btks    How did you find that?  Have to buy stock in Intuit?

Thanks IRonMan...They didn't have the valuation on the timber done...  Most properties in our area of northern MI don't...  But I appreciated the response it was helpful.

Thanks George4Tacks.  This was helpful and gave us some areas to discuss with our client.  

Thanks again George4Tacks.  this is pretty much how we solved the issue.  The one thing I found in working this problem out was that stumpage is slightly different from timber in most of the lititure...  anyway the recommendation from Purdue (from your link) was this

Net gain (loss) = sale proceeds -  allowable basis - sale expenses

thanks again for the help