<prompt> Human: As the title states, I received a letter in the mail from the IRS that my tax return from 2014 was incorrect and that I owe around 2.5K on less than 10K disputed income. However, when I go to check my balance online on the IRS site it says I owe nothing. Even when I go to the online payment application section, it says the service is unavailable for me. Really unclear about what I should do. I cant really afford that amount at the moment, not that it would ever be convenient. Thank you in advance for any help.  <response>: The letter is probably a CP2000 or its kind. The reason you dont owe more online is because you can dispute the income or correct your return to show the income and expenses if applicable. So right now its just a letter stating assumed changes to your tax. The main thing to do is respond, you can call 1-800-829-1040 which is the main hotline. But you will have to send in a signed response to the questioned income. Either in a letter form or amended return. A nonresponse is an agreement to the proposed change. 