I got shares of a private S-corp with minimal value. Is there a place to declare this on my return, or do I need to fill out a separate form independent of a tax return?

[miclarson-gmail-]

This is a new Delaware startup without any formal valuation, so shares are essentially worthless at this point.

[KrisD15]

How did you get them, as compensation? 

Usually the basis is the value that was reported as income on your W-2.

If nothing was reported as income, you would only report the sale at which time the basis in the stock would be zero.