A source close to the couple tells us the two are "still friends" and they maintain a business relationship with each other. In fact, sources tell us ... no lawyers are involved.
The couple has one child together.
David and Courteney met on the set of "Scream" sometime around 1995 ... and were married in 1999. They are currently co-starring in the upcoming "Scream" movie due out next year.
There was a hint of things to come back on September 25 when Arquette was spotted out, sans wedding ring.
UPDATE: The couple has released a statement saying, "We have agreed to a trial separation that dates back for some time. The reason for this separation is to better understand ourselves and the qualities we need in a partner and for our marriage."
The statement continues, "We remain best friends and responsible parents to our daughter and we still love each other deeply."