Information For...

For you and your family
Standard mileage and other information

Forms and Instructions

Individual Tax Return
Instructions for Form 1040
Request for Taxpayer Identification Number (TIN) and Certification
Request for Transcript of Tax Return


Employee's Withholding Allowance Certificate
Employer's Quarterly Federal Tax Return
Employers engaged in a trade or business who pay compensation
Installment Agreement Request

Popular For Tax Pros

Amend/Fix Return
Apply for Power of Attorney
Apply for an ITIN
Rules Governing Practice before IRS

Understanding your CP521 Notice


We're reminding you that you have an installment agreement payment due. Please send your payment immediately.

What you need to do

  • Read your notice carefully. It's a reminder to send in your monthly payment.
  • Pay by the due date. Go to the payments page to find out more about your payment options.


Answers to common questions

What is the notice telling me?
Your monthly installment agreement payment is due to us by a specific date.

What do I have to do?
Pay the amount due shown on the notice. Mail us your payment in the envelope we sent you. Include the bottom part of the notice to make sure we correctly credit your account.

What happens if I don't pay?
If you don't send us a payment, the interest and penalties you'll have to pay will increase and you could default on your installment agreement.

Who should I contact?
If you have any questions, call us at the number at the top of the notice. A customer service representative will assist you.

Printable samples of this notice (PDF)

How to get help