I just received a letter from the IRS saying I have an amount past due from my 2020 taxes, but I paid the full amount in March. Is this a scam?

[fopmakabob]

They said they recently contacted me about past due 2020 taxes, but they did not. I'm confused about what this could be. It appears to be a legitimate IRS address, etc., except the payment address is for Cincinnati, which is not the processing center for my region of the country.

[pjd0501]

Hey, I posted similar question here: https://ttlc.intuit.com/community/after-you-file/discussion/received-irs-notice-[product key removed...

I don't have any address as such, but the notice date is July 5, 2021 (which is a week away from now)!!