Credit: Paul Morigi/FilmMagic

What a way to start the new year.

According to divorce documents that musician Ben Harper filed Friday, he separated from actress Laura Dern on New Year's Day.

Oddly, the two -- who have a son, Ellery, 9, and a daughter, Jaya, 5 -- have been living and traveling together all this year.

What gives?

TMZ reports the reason is because of money: When a couple is legally separated, their earnings become separate.

The site points out that Harper, 40, likely out-earns Dern, 43.

The two cited irreconcilable differences for their split.

Both are seeking joint custody of their two children.