If there were alive in 2020, they are entitled to the RRC.

Lisa: DOD was 7/18/20. So she would get the 1200.00 for 2020 but not the 600.00 that we received in 2021?

Entitled to full credit, subject to income limits, less amount already received.

"So she would get the 1200.00 for 2020 but not the 600.00 that we received in 2021?"

There is no Splitting of the tax year. Alive on Jan 1, 2020 = qualifies for whatever was made available, given the income limitations, SSN requirement, etc.

Perhaps it would help to review what is really happening:

The funds were paid out as Advanced payment against a projection. The projection used 2018 or 2019 tax returns. But 2020 is the 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 entitled to the payment/credit as individual filers. That doesn't mean "not being claimed." It means "no longer qualifies as a dependent."

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

Interactive wizards portal 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

One for each EIP.

Alive even one day in 2020, entitled to the full RRC for 2020.