In the legal documents, obtained by TMZ.com, the Beautiful hitmaker cites "irreconcilable differences" as the reason for divorce and claims they split on 11 September (10).
She has hired top celebrity divorce lawyer Laura Wasser to represent her.
The petition states the former couple signed a pre-nuptial agreement when they wed in November 2005 and Wasser asks for the "earnings and accumulations of (Aguilera) before marriage, during marriage and from and after the date of separation" be considered separate property.
The singer is seeking joint legal and physical custody of their two-year-old son Max, while she is also requesting a judge deny Bratman the opportunity to claim spousal support.
Wasser's celebrity clients also include Mel Gibson's soon-to-be ex Robyn Gibson, actress Patricia Arquette and R&B singer Kelis.