I made an honest error on my tax returns some years ago. I was billed plus interest. I did not complain as it was my error and just a few hundred dollars. I paid and everyone else should pay also.
I use an accountant now.
On the other hand, I made a arithmetic error in my returns one year. About 3 year later, I got a letter and a check from the IRS stating I had made an error in my returns and the check covered the amount of the error and accrued interest for 3 years.