QDRO mistake

My ex husband requested a distribution from my pension.   He was allowed as we had signed a QDRO.  However when my employer calculated his lump sum, they calculated it for 29 years of my employment.  The QDRO that we signed said the calculation should have only been for 19 years( while we were married). So they gave my ex too much money.  What is my recourse?  

Why do you think you need recourse?

First check with the plan administrator about your benefit. If it is not what it should be, then you need to file a claim for benefits.  You should be able to do that without starting payment. If your benefit is improperly reduced because of the mistaken calculation of the AP benefit, then you will need to proceed through the claims procedures to get a correction.

If your benefit was not adversely affected, overpayment to your ex is not your concern.

Clarification:  You MAY need to file a claim for benefits. The plan administrator may correct any improper reduction in your benefit informally based on having the mistake pointed out.  Then it is the plan administrator's separate concern about the overpayment.