The actors, who play brother and sister on the hit drama, confirmed earlier this week (14Dec10) they had split after two years together.
Carpenter moved to officially end the marriage on Thursday (16Dec10), when she filed divorce papers in Los Angeles Superior Court, and the documents reveal the pair actually parted ways back in August (10).
She lists the date of separation as 9 August, 2010, citing "irreconcilable differences", reports TMZ.com.
The actress is asking for spousal support and legal costs.
The couple has no children.
The divorce papers were lodged on the same day their Dexter co-star Julia Stiles was forced to blast rumours she had been romantically involved with Hall, insisting she had "absolutely nothing to do" with the breakdown of their marriage.