Hello and thanks you for using Just Answer. The IRS can withhold a joint return if one spouse owes past-due child support. A spouse not required to pay the past-due amount may received all or a portion of the couple's refund by filing Form 8379, Injured Spouse Allocation www.irs.gov/pub/irs-pdf/f8379.pdf, .
The IRS calculates the injured spouse's refund as follows:
1 Each spouse's tax is calculated as if they filed separately.
2 The injured spouse's separated tax is divided by the total tax for both spouses calculated separately.
3 Percentage from step 2 is applied to the couple's actual joint tax liability to get the injured spouse's share of tax.
4 The injured spouse's payments are subtracted from the tax.