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IRS Notice CP521: Payment Reminder

Notice CP521 is a monthly reminder of your upcoming installment agreement payment. If you have an active IRS installment agreement and your payment is made by mail or check (not direct debit), the IRS sends CP521 as a reminder each month. C

By Michael Brennan·3 min read·Updated April 23, 2026
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Notice CP521 is a monthly reminder of your upcoming installment agreement payment. If you have an active IRS installment agreement and your payment is made by mail or check (not direct debit), the IRS sends CP521 as a reminder each month. CP521 is routine — it is not a warning of problems. Taxpayers on direct debit installment agreements typically do not receive CP521.

If you cannot make the payment

If you cannot make an upcoming installment payment, contact the IRS before the due date. Options include: requesting a short skip (limited availability), modifying the agreement to a lower monthly amount, or converting to a different resolution type if your financial situation has materially changed. Missing payments leads to CP523 — default of the agreement — which has much more serious consequences.

Staying in good standing

To avoid default: make each monthly payment on time; file all required tax returns on time; pay any new tax liability that accrues; keep the IRS informed of address changes. A single missed payment can be cured in most cases; chronic missed payments or new tax debts lead to agreement default and CP523 issuance.

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Frequently asked questions

Do I need to respond to CP521?+

No — CP521 is a routine monthly reminder. If you make your payment on time, no response is needed. Only respond if you cannot make the payment or have other issues with your agreement.

Why did I get CP521 but not others with installment agreements?+

CP521 is primarily sent to taxpayers paying by mail or check. Direct-debit installment agreement holders typically do not receive it because payments are automatically pulled.

What if I missed a payment?+

Make it up immediately if possible. Missing one payment rarely causes immediate default, but repeated misses or non-response lead to CP523 default notice. Call the IRS if you cannot catch up.

About the author

M

Michael Brennan

Senior Tax Policy Writer · Fresh Start Division Editorial

Michael Brennan is a Senior Tax Policy Writer at Fresh Start Division, focusing on IRS collections procedure, the IRS Fresh Start Program, and federal tax policy. Michael has written extensively on tax resolution for American taxpayers.

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