In plain English, the IRS is very backed up on mail. Mail-in returns, mailed payments, etc. So backed up that sometimes by the time they process your payment, you have already canceled the check or their system has automatically sent you another notice of an amount not paid. Remember that these are automatic generated notices. If you receive one but you have already sent in payment, be patient. Don’t cancel your check, and don’t panic. If possible, efile and pay online if you can. If not, mail certified.
This news post from the IRS is dated Aug 21, 2020 and has more details on the mail processing situation going on right now:
https://www.irs.gov/newsroom/irs-temporarily-stops-mailing-notices-to-taxpayers-with-balances-due
Written by Laura Fleig
September 16, 2020