if the IRS tried to calculate everyone’s taxes for them
The IRS does calculate everyone’s taxes without an audit. If you mistype a bank statement you will get a bill or a check from the IRS (depending on whether the error was paying too much or too little).
An audit is completely different than the typical, "you typed $1000 in bank interest but you only really received $100 so here’s a check for the difference in taxes. This has happened to me many times over the years. It’s why I no longer get stressed over taxes because I know the IRS will just send me a bill or a check in 6 months to fix any mistakes.