For the 3rd stimulus payment, what happens if my 2020 return is processed after IRS sends the stimulus check

[yjchyan]

My family's income in 2020 decreased compared to my income in 2019. Our 2020 income is below the $150,000 threshold, while our 2019 income is above.

However, the IRS sent me the stimulus check before my 2020 return is processed, so they used my 2019 income information, which results in a significantly lower amount in the check.  Question: Will IRS send another payment to me to make up the difference between what my payment should have been if based on my 2020 return?

[VolvoGirl]

If they do it like the first 2 rounds then it will be reconciled on your 2021 return next year.  So it might be based on 2021 income and not 2020.  

[yjchyan]

For 2nd stimulus payment, it would make sense because it was distributed in January, and tax season was coming. For 3rd stimulus, if they follow the same suit, that would be messed up, because it is only March, and I have to wait for a whole year to claim the missing amount?