The IRS has made a change to your return based on a miscalculation or erroneous entry on your return. Often, this is because of information you gave them or they received from third parties, such as your Bank, your Employer, or a Lender. It may be that a social security number was incorrect on the return. It may also mean you receive more money than you thought. The notice is similar in effect to the CP11.
Respond to Notice CP16
If the Notice states you will be receiving a greater refund, then no further response should be necessary. But, if the Notice indicates that you owe taxes or your refund was reduced, look carefully at the (obscure) reason given for the adjustment. Then, look at the line of your return being adjusted to see if any problem is apparent.
If you disagree with the IRS please follow the Prep Steps for IRS Notice CP 16 and see Mr. Hopkins in Colorado Springs, Pueblo or Denver before proceeding. You only have 60 days to respond.
Be careful about what you say and send to the IRS. These will be used against you! Also, after you respond, don't be surprised if you get a Letter 86C transferring the file to another office or, a Letter 2645C asking for more time! However, you must follow up. Don't depend on the IRS!