The date on which a debtor files a petition for relief under the Bankruptcy Code and commences its bankruptcy case. This date is used to determine what is property of the estate and is the date by which creditors' claims are measured. Events or claims occurring before the petition date are considered to have occurred prepetition, and events or claims occurring after the petition date are postpetition. Many look-back periods concerning prepetition activity, such as preferences or fraudulent conveyances, are tied to the petition date. The debtor is protected by the automatic stay from the petition date.

For more information about the petition date, see Practice Note, Bankruptcy: Overview of the Chapter 11 Process.