Did this bonus result in compensation included on your W-2? If so, the compensation, (assuming you paid nothing for the stock), is the basis for the GROSS amount of stock you received, before stock withheld or sold "for taxes."
If the company is no longer active and you sold before that event, you may actually have a capital loss to report here. As is often the case in this forum, that lack of substantive details makes the situation vague, at best.
