Amending a Return to Claim a Dependent

[amberduhh]

Hi! I just learned that in custody cases, the noncustodial parent can only claim the dependent if they paid all of their child support/arrears for that year. Of course, I noticed this rule after I filed, and after my ex filed as well. I allowed him to claim our son this year, as that's what the court order says (we alternate years). But I just got a letter back from the courts stating he is almost $1000 in arrears for 2019, so I've just mailed in my amended returns and claimed our son as my dependent. (He has lived with me the whole 12 months, I have paid all of his expenses, his father has not paid all child support) Once my amended return gets approved, what happens to the $2000 his father already got back for claiming our son? Will they ask him to give it back, or would they just take it back from him next year when he files? 

[Critter]

If 2 people claim the same dependent  then the IRS will send out letters to both parties requesting the incorrect party to amend their return.  If neither party amends then the IRS will send out second notices requiring both parties to prove their right to claim the child and then the IRS will decide who was wrong and the incorrect party will need to pay back the incorrect refund with penalties and interest attached.