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)

Need Help?

  • You can authorize someone to contact the IRS on your behalf.
  • See if you qualify for help from a Low Income Taxpayer Clinic.
  • If you can’t find what you need online, you can call the IRS at the 800, 866, or 888 number listed on the notice.