Filing a bankruptcy petition creates an estate that includes all legal and equitable interests of the debtor, including contingent interests that are "sufficiently rooted in the prebankruptcy past." Several factors might be important in deciding whether a specific bonus payment is estate property, including whether the right to receive it was vested at the time of the petition, whether the employer had any discretion to pay it, etc. One case discussing the issues is In re Edmonds, 263 B.R. 828 (D. Mich. 2001). This is an issue I would expect to have to litigate if it came up in one of my cases.