I found the issue - the IRS sent the advance payments for each parent and I never saw my wife's 6419. So the $500 net due is correct.Thx.

Well, the IRS link for Line 5 Worksheethttps://www.irs.gov/instructions/i1040s8#en_US_2021_publink100077560shows that they subtract 2000 from 3000 to get 1000 (...