You cannot get that withholding back. A QDRO (Qualified
Domestic relation order) makes the 401k distribution not subject to the 10%
early (before age 59-1/2) penalty (called an additional tax on line 59 of form
1040). But the distribution is not exempt from regular income tax. You must report the
income distribution, and tax withholding, on your tax return. You will receive
a form 1099-R from the plan administrator in late January or early February.
If your real issue is that you think the other parent should
have paid the tax, instead of you, you’ll have to take that up with the court.
If your name and SS# are on the 1099-R, the IRS will expect you to report it.