Happiness is:
Get letter from IRS saying you owe $$$$$$$$$$$ which should not be the case.
Call IRS and be told wait time is up to one hour.
Try IRS.gov site as recommended.
Creating an account is a PITA but not that bad.
Click 'view balance.'
Answer: 'You owe $0.00'
Think 'wtf? but I'll take it.'
At my age letters like this one could kill me, you'd think the government would know that.