I got a letter like that. It was saying that my second stimulus was not fully
paid, but I could claim it on my tax return. I think I only got like $600 on the second stimulus check. The truth was, I could not claim the $3,300 they said I should have gotten on the second stimulus because I was not eligible after 2019. So, I waited for the third stimulus check to hit my bank, and then filed my 2020 tax return with no credits for the second stimulus. How, you may ask did I get a third stimulus if I couldn’t take a credit on my 2020 taxes? Easy, they sent the third payment before filing was due for 2020. My 2019 filing only include part of the year my wife worked full time from 2018. Since everything was based off of 2019, I qualified. Since there was no claw back, I waited to file 2020, when my wife had worked full time for a year, knowing I wouldn’t qualify for the third stimulus if I filed early. Does that make me a bad person? Maybe. But, I’m just playing the hand I was dealt (Four Aces).