Tax Accounting Question:

When a private company issues stock to an independent contractor as compensation instead of cash, and no fair market value was given to the contractor on the date the stocks were granted. The contractor decides to an 83(b) election, but does not have the necessary info to complete the election worksheet, namely, missing the fair market value of the stocks on date of grant.

Who's responsibility is it to come up with a fair market value? The private company that issued the stock or the independent contractor?

I assume it is the companies obligation but I could not find my answer online. Please help. Thank you.