IRS Notice CP521: Missed Payments and Reinstatement

IRS Notice CP521 is the monthly reminder that your installment agreement payment is coming due. It shows your current balance, the amount to pay this month, and the date the payment must reach the IRS. It is not a default notice, not a warning, and not a threat of levy. Pay the amount shown by the date printed on the notice and your agreement stays on track.¹

You may see the same notice in Spanish (CP521 SP), or a version labeled CP621 for certain business accounts. All three do the same job.

CP521 vs. CP523: Know Which One You Have

Before you do anything else, look at the notice number in the corner. CP521 is a bill. CP523 is trouble. CP523 is a Notice of Intent to Levy telling you the IRS has determined you defaulted and plans to terminate your installment agreement in 30 days unless you fix the problem.²

If yours says CP521, you are still in good standing. Read on. If it says CP523, jump to the section on terminated agreements.

How to Pay by the Due Date

The IRS gives you several ways to make the payment shown on CP521:

Log in to your IRS online account at irs.gov to see your balance, scheduled payments, and payment history, and to submit payment electronically.³
Mail a check or money order using the payment stub attached to the notice, to the address shown on the stub.
If your agreement uses automatic bank withdrawals, confirm the payment is scheduled. If it does not, you can convert to a Direct Debit Installment Agreement through the IRS Online Payment Agreement tool, which cuts the risk of a missed payment.⁴

If the amount looks wrong, or you already sent a payment that may not have posted yet, call the toll-free number printed on the notice before the due date. Don’t skip the payment on the assumption that the IRS made a mistake.

If You Cannot Afford This Month’s Payment

Call the number on the CP521 notice, or use the Online Payment Agreement application, before the due date passes.⁵ The IRS can lower your monthly amount, extend the payoff timeline, or in some cases suspend payments temporarily.

Restructuring the agreement online costs $10. By phone, mail, or in person, it costs $89.⁶ A restructured agreement is always cheaper than a defaulted one.

There is a real financial reason to keep the agreement alive. The failure-to-pay penalty runs 0.5% of your unpaid balance per month at the standard rate, but drops to 0.25% per month while you have an approved installment agreement in place and filed your return on time.⁷ Default the agreement and you lose that discount for the months you were out of compliance.

What Else Can Void the Agreement

Paying on time is necessary but not sufficient. Federal law lets the IRS modify or terminate an installment agreement for any of these reasons:⁸

Missing a monthly payment. Even one late installment counts as a breach.
Owing new tax you don’t pay on time. If you file this year’s return with a balance due, that balance has to be paid by the filing deadline. A new unpaid liability violates the agreement.
Failing to file a required return, even one where no tax is owed.⁹
Not providing updated financial information when the IRS asks for it. The agency can request a new Collection Information Statement at any point.
A significant improvement in your finances. If the IRS finds your income has gone up substantially, it may require higher payments or end the current agreement.

Any of these can put you on the path to a CP523 even if you never missed a payment.

What Happens If You Ignore CP521

A single missed payment does not end the agreement immediately, but the clock starts. The IRS sends follow-up notices, and if the miss goes unresolved you eventually receive CP523. That notice states the IRS intends to terminate the installment agreement and begin levy action, and it gives you 30 days from the date of the notice to fix the problem or appeal.¹⁰

Federal law requires that 30-day written warning before the IRS can terminate the agreement, along with the reason for the termination.⁸ Within that window you can pay the past-due amount, file any missing return, or call the IRS to negotiate. If you have already taken corrective action, call anyway to confirm the IRS has recorded it before the deadline.²

Collection Once the Agreement Is Gone

When the 30 days lapse, the full remaining balance plus accrued penalties and interest becomes due at once. The IRS can then levy money from bank accounts, garnish wages, and seize and sell vehicles or real estate.¹¹ Wage levies continue paycheck to paycheck until the debt is paid or a new arrangement is in place.

The IRS can also file a Notice of Federal Tax Lien, a public record of the government’s claim against your property that makes it hard to sell real estate, refinance, or get credit.¹²

And if your total tax debt with penalties and interest exceeds $66,000 (a threshold that adjusts annually for inflation), the IRS can certify you to the State Department as seriously delinquent, which can lead to denial or revocation of your passport. Taxpayers making timely payments under an installment agreement are exempt from that certification; default removes the exemption.¹³

Reinstating a Terminated Agreement

If the agreement has already terminated, reinstatement is possible. You need to be current on all filing obligations, resolve whatever caused the default, and pay a reinstatement fee. Online, the fee is $10. By phone, mail, or in person, it is $89. Changes to an existing Direct Debit Installment Agreement cost nothing.⁶

If reinstatement is not available, you can apply for a new agreement using Form 9465, and the IRS may require a Collection Information Statement (Form 433-F) covering your income, expenses, and assets.¹⁴¹⁵ Setup fees for a new agreement run higher: $22 for direct debit applied online, $107 for direct debit by phone or mail, $69 for a standard online setup, and $178 by phone or mail without direct debit.⁶ The new terms may be stricter than your old ones, including higher monthly payments or mandatory direct debit.

Whenever you call the IRS, write down the representative’s name, employee ID number, the call reference number, and exactly what you were told to do. If a dispute comes up later about what was agreed to, those notes are your protection.

If You Believe the IRS Is Wrong

If CP523 arrived and you believe there was no default, you can appeal through the Collection Appeals Program by filing Form 9423 within 30 days. Send it to the IRS office that issued the notice, not directly to the Office of Appeals.¹⁶

Reduced Fees for Low-Income Taxpayers

If your adjusted gross income is at or below 250% of the federal poverty guidelines, you qualify for reduced or waived installment agreement fees. For 2026, that means a single person earning $39,900 or less, or a family of four earning $82,500 or less, with higher thresholds in Alaska and Hawaii.¹⁷

Qualifying taxpayers who use direct debit get the setup fee waived entirely. For other payment methods, the fee drops to $43 and is reimbursed once the agreement is complete. File Form 13844 within 30 days of receiving your acceptance letter. Applications filed after that window will not be considered.

1
Internal Revenue Service. Understanding Your CP521 Notice
2
Internal Revenue Service. Understanding Your CP523 Notice
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Internal Revenue Service. Payments
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Taxpayer Advocate Service. Notice CP521 – Monthly Installment Agreement Payment Reminder (SB/SE Notice)
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Internal Revenue Service. Online Payment Agreement Application
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Internal Revenue Service. Payment Plans; Installment Agreements
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Internal Revenue Service. Failure to Pay Penalty
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Office of the Law Revision Counsel. 26 USC 6159 – Authority to Enter Into Agreements
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Taxpayer Advocate Service. Payment Plans (Installment Agreements)
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Internal Revenue Service. Notice CP523
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Internal Revenue Service. Levy
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Internal Revenue Service. Understanding Your CP504 Notice
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Internal Revenue Service. Revocation or Denial of Passport in Cases of Certain Unpaid Taxes
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Internal Revenue Service. About Form 9465, Installment Agreement Request
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Internal Revenue Service. Instructions for Form 9465
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Internal Revenue Service. Form 9423, Collection Appeal Request
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Internal Revenue Service. Form 13844, Application for Reduced User Fee for Installment Agreements