Jessica Alba has filed for divorce from Cash Warren ... and speaking of cash, sources in the know tell TMZ, there's no prenup.

Jessica and Cash announced their split back in January, but they made it official Friday. Jessica filed her docs, with the help of disso queen Laura Wasser, and Cash filed immediately thereafter with the help of attorney Adam Lipsic. His docs mirror hers.

Our sources say the divorce is "extremely amicable."  They're both asking for joint physical and legal custody of their kids, ages 16, 13 and 7.

As for their assets, it's all community property ... and there's A LOT. Jessica's Honest Company is valued at $623 million. As for Cash, he co-founded Pair of Thieves -- an underwear and sock company -- and it's valued at around $100 million, but one of our sources says it's worth way more than that. There are many other assets as well.

Cash was out and about Tuesday with one of his kids -- without his wedding ring -- and he looked chill.

J&C list the date of separation as December 27.

They married in 2008. In Hollywood, that's a pretty solid run ...