Thanks @DianeW777 indeed my W2 has box 12 codes C, M, and N. (C for COGLI, M for uncollected SS tax, and N for Uncollected Medicare tax. The numbers agree with 6.2% and 1.45% of the COGLI amount.
In my W2/W2G Summary form in Turbotax, lines h and i have the correct amounts corresponding to the W2 box 12 codes N and M respectively.
I had not changed anything before checking the W2 & W2G Summary form - so my W2 was imported/entered correctly and the numbers match; our 1040 should be correct.
The pop-up dialog about Notice 2020-65, and expecting a W2-C doesn't apply to our situation, and it would be good to add some logic to detect this and avoid the pop-up for situations like ours. Or perhaps add some words like "Note: Retirees who receive a W2 from their former employer reporting COGLI with codes C, M, N in box 12 may see this pop-up and can ignore it if they have no deferred social security tax other than what is reported in box 12 with code M"
