Letter 131C is a curious notice from the IRS. It essentially states that they are not going to help you. The letter often requests that you provide them additional information but they don't specify what more information they desire.
Respond to Letter 131C
You can call the 1-800 number shown in the letter but without your knowledge of the problem they likely won't be able to help you. So, if you know to what the IRS is referring, you can follow the Prep Steps - Other Problems and respond accordingly.
If you do not know what the problem is, you should order your transcripts. Review the transcripts in detail for a problem. Then, call the IRS and ask them to explain the situation. Have your tax returns available when you call and be sure to ask lots of questions.
At the very least, follow the Prep Steps and order your Account Transcripts and Wage & Income Transcripts. Then, when you call them back, you'll be ready.
