stimulus checks

The reconciliation on the 2020 return has nothing to do with when they received the payment.

No one received the second payment in 2020 as they started distributing them January 4 2021.

Enter the amount received, nowhere does it ask when they received it.

you enter the second payment on Line 19 of the RRC worksheet, doesnt matter when they got it.

You just stated this as circular: "but received his/her second in January, how do you not take the credit for not receiving the second stimulus check"

They Got it, according to you. Receiving it in Jan, means Got It. Not "take the credit for NOT receiving."

Perhaps it would help to review what is really happening for EIP “stimulus” funds: The funds were paid out as Advanced payment against a projection. The first two payouts were projected based on 2018 or 2019 tax returns, but the eligibility is part of tax year 2020 as Actuals. You use the 2020 return to reconcile what a person is entitled to, against what they got.

If the person is not a dependent in 2020, then they would be eligible for consideration as individual filers. That doesn't mean "not being claimed." It means "no longer qualifies as a dependent." You must correctly address whether they Can be Claimed as a dependent on someone else’s tax return.

The third payout which started in Jan 2021, has different eligibility rules as to dependents and this payout is a projection, using 2019 or 2020 tax returns, then reconciled against Actuals on the 2021 tax return.

You might want to bookmark these links and read the IRS guidance.

Interactive wizards portal includes one for determining dependency:

https://www.irs.gov/help/ita

And:

https://www.irs.gov/newsroom/economic-impact-payment-information-center-topic-a-eip-eligibility

https://www.irs.gov/coronavirus/second-eip-faqs#Eligibility

https://www.irs.gov/newsroom/irs-is-issuing-third-round-of-economic-impact-payments

One for each of the three EIP “stimulus” payments.