@abctax55 "You can't just make an estimated payment now/Jan 15, 2021 and have the penalties eliminated"

I had two separate clients call me this week about selling rental properties in November or December with a large capital gain.  If the extra income is received in the fourth quarter, the final payment can be more than the first three.

For one of these clients it was better to make the state payment (not CA) before the end of the year, because they will still be below the SALT limit of $10K.