The actress called time on her relationship with the 'Manchester By the Sea' star back in March 2016 but they have now made their split official by submitting court documents to end their marriage.
The documents, which were filed on Monday, show that Summer is citing ''irreconcilable differences'' as the reason for the split and is asking for joint legal and physical custody of their children, Indiana, 13, and Atticus, nine. Summer is also requesting spousal support, according to E! News.
Casey and Summer tied the knot back in 2006, having met in 1995 thanks to Summer's brother Joaquin Phoenix, who was working with Casey's sibling Ben on 'To Die For'. The former couple got engaged in 2003 and welcomed two children together.
When the pair split last year, they issued a joint statement to insist they had ''amicably'' gone their separate ways.
The spokesperson confirmed: ''Casey and Summer have amicably separated. They remain very close friends.''
Whilst a source added at the time: ''She was having a lot of trust issues. They went to couples counselling but they just couldn't recover.''
Meanwhile, Casey previously admitted he is unsure whether the breakdown of his marriage - which was coming to an end during filming for 'Manchester By the Sea' - had any impact on his performance.
He shared: ''I don't know. It sounds crazy, I acknowledge that, but your body doesn't really know the difference between experiencing something for real and convincing yourself you're experiencing something.
''Are you in a dark place in your personal life and it helps make the movie? Or do you put yourself in that place in order to make the movie?''
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