If you made a mathematical error on your return, often times the IRS will automatically fix the error.  After correcting the mistake, the IRS will send you a notice that shows the changes made to your return (usually a CP11 or CP12).  Before correcting your return for a mathematical error, you may want to call the IRS at 1-800-829-1040 to see if they have fixed it for you.

If you forgot to include a form or schedule to your return, it is very likely that the IRS will send you a notice requesting just the missing form(s) and/or schedule(s) which means you will not need to do anything other than send in the requested items.