ARPA provision -  EIC for 2021 taxpayer may choose to use 2019 earned income if it is greater then 2021 earned income       If single in 2019 but MFJ for 2021 - the total of each (taxpayer+spouse) income for 2019 is used

This information is available in resource material such as 1040 Quickfinder.  It is also in the Handbook issued with my CPE seminar.