So if you get a notification in the mail that your personal tax return is being audited, you have several options. The first thing you should probably do is send the notice to the accountant who prepared your tax return and ask for their advice.
If you prepared your own tax return then I would look at the notice and try to figure out if it’s something substantial and significant that you’re concerned about. If it’s something more ordinary such as substantiating an expense and you have the receipt, you can just mail it back to the IRS.
If it’s something more significant. I would definitely either talk to your accountant or find an attorney to help you handle the audit with the IRS.