When your taxes are e-filed, the IRS computer systems do a quick verification to make sure the basic information matches their records (for example, birth dates and Social Security Numbers). After the return has been accepted, it will be reviewed further by the IRS. If the IRS feels that something is missing or incorrect, they will adjust the return and send you a letter explaining what they did, and why. If the adjustments they made result in your owing additional taxes, the letter will indicate the amount due. If the adjustments result in your owing less money, they will send you a check for the amount they owe you. In most cases, the letter will also include information on how to dispute the changes they made.