federal income tax refund for arrears

When a federal income tax refund is used to pay arrears of child support, does it include the Earned Income Credit or only the amount of the refund from actual income (wages)? Also, how are the amounts of a married couple's return seperated when one spouse owes child support arrears?

Refund

The full refund, however it is calculated, is applied against the support.

I believe, if you file a joint return, the fact that only one spouse owes support will not prevent the refund from being applied. The way around that is to file separate returns.