IRS notices and letters, explained

By Mahruf, founder of Main AI · Last verified 2026-10-01 against the official text · How we source and verify

Find the code in the top or bottom corner of your notice. Each entry below says what the IRS says it means and what deadline applies, with a link to the IRS’s own page.

Code	What it is	Deadline
4883C	The IRS says it received a return under your SSN or ITIN and, to protect you from identity theft, needs you to verify your identity and the return before processing.	The date printed on the notice, or as soon as possible.
5071C	The IRS says a return was filed under your SSN or ITIN and it needs you to verify your identity and the return.	The date printed on the notice, or as soon as possible.
5747C	The IRS says it received a return under your SSN or ITIN and needs you to verify your identity and the return, possibly at a Taxpayer Assistance Center.	The date printed on the notice, or as soon as possible.
CP05	The IRS says it needs more time to verify your income, withholding, tax credits and/or business income, and asks you to allow up to 60 days.	The date printed on the notice, or as soon as possible.
CP05A	The IRS says it needs more supporting documentation to verify your income and federal tax withholding before it can issue your refund.	The IRS page does not give a fixed number of days; the deadline is the date printed on your notice. The IRS says to gather the required documentation and reply by the date shown on your notice, preferably with the Document Upload Tool.
CP11	The IRS says a CP11 means it corrected one or more mistakes on your return and, as a result, the amount you owe changed.	The IRS page does not give a fixed number of days; the deadline is the date printed on your notice. The IRS says if you do not contact it by that date, you lose formal rights to have the changes reversed and your right to appeal to the U.S. Tax Court.
CP12	The IRS says a CP12 means it corrected one or more mistakes on your return, and you are now due a refund or your refund amount changed.	The IRS page does not give a fixed number of days; the deadline is the date printed on your notice. The IRS says if you do not contact it by that date, you lose formal rights to have the changes reversed and your right to appeal to the U.S. Tax Court.
CP14	The IRS says it sends a CP14 because you owe money on unpaid taxes.	The IRS page does not give a fixed number of days; the deadline is the date printed on your notice. The IRS says you are not charged interest if you pay in full by the date on the notice, but interest accrues on the unpaid amount after that date.
CP22A	The IRS says it sent a CP22A because it made changes to your tax return and you owe because of those changes.	The IRS page does not give a fixed number of days; the deadline is the date printed on your notice. The IRS says interest will accrue if you do not pay the full amount by the date on the payment coupon.
CP49	The IRS says a CP49 means it used all or part of your refund to pay a tax debt.	The date printed on the notice, or as soon as possible.
CP59	The IRS says a CP59 means it has no record that you filed your prior year personal tax return.	The date printed on the notice, or as soon as possible.
CP71	The IRS says a CP71 means you still have an unpaid balance that needs immediate attention, and it explains that the State Department may deny or revoke a passport for seriously delinquent tax debt.	The date printed on the notice, or as soon as possible.
CP71C	The IRS says a CP71C means you still have an unpaid balance that needs immediate attention, and it explains that the State Department may deny or revoke a passport for seriously delinquent tax debt.	The date printed on the notice, or as soon as possible.
CP80	The IRS says this notice means it credited payments or other credits to your account for the form and period shown, but has not received your tax return.	The date printed on the notice, or as soon as possible.
CP88	The IRS says it is holding your refund because you have not filed one or more returns and it believes you may owe tax.	The IRS page does not give a fixed number of days; the deadline is the date printed on your notice. The IRS says if you filed within the past eight weeks you do not need to do anything now.
CP90	The IRS says a CP90 means it intends to levy certain assets for unpaid taxes and is informing you of your right to a Collection Due Process hearing.	IRS Publication 1660 says a Collection Due Process hearing request must be postmarked on or before the 30th day after the date of the levy notice.
CP91	The IRS says a CP91 means it intends to levy up to 15% of your Social Security benefits for unpaid taxes.	The date printed on the notice, or as soon as possible.
CP161	The IRS says a CP161 means you have an unpaid balance due, and the notice explains how the amount was calculated.	The IRS says to contact it within 10 days of the notice date if you think it made a mistake, and to pay by the date on the notice.
CP297	The IRS says a CP297 notifies you of its intent to levy certain assets for unpaid taxes and of your right to a Collection Due Process hearing.	IRS Publication 594 says you can request a Collection Due Process hearing within 30 days from the date of your Notice of Intent to Levy and Notice of Your Right to a Hearing.
CP501	The IRS says a CP501 is a reminder that you owe a balance because it has not received your payment or a response to a previous notice.	The IRS page does not give a fixed number of days; the deadline is the date printed on your notice. The IRS says to pay by the due date shown on the notice and to include the bottom part of the notice with a mailed payment.
CP503	The IRS says a CP503 is your second reminder that you still owe a balance because it has not received your payment or a response to previous notices.	The IRS page does not give a fixed number of days; the deadline is the date printed on your notice. The IRS says you must pay the entire balance by the due date shown to avoid additional penalties and interest.
CP504	The IRS says a CP504 is your Notice of Intent to Levy under Internal Revenue Code section 6331(d), sent because it has not received payment of your unpaid balance.	The IRS page gives no fixed number of days; it says the notice is a final reminder of intent to levy wages, bank accounts, or a state tax refund, and to avoid this you must pay immediately.
CP504B	The IRS says a CP504B is a notice of intent to levy under Internal Revenue Code section 6331(d), sent because it has not received payment, and it may also file a Federal Tax Lien.	The IRS says to pay or contact it as soon as possible but no later than 30 days from the date of the notice.
CP508C	The IRS says it has certified your seriously delinquent tax debt to the State Department, so your passport may be revoked and new or renewal applications denied.	The date printed on the notice, or as soon as possible.
CP523	The IRS says a CP523 means you defaulted on your installment agreement and it intends to terminate the agreement and levy your assets.	The IRS says to contact it as soon as possible but no later than 30 days from the date of the notice.
CP2000	The IRS says a CP2000 means income or payment information it received from third parties, such as employers or banks, does not match your return, and the difference may raise, lower, or not change your tax.	The IRS page does not give a fixed number of days; the deadline is the date printed on your notice. The IRS says to reply by the date listed, completing and signing the response form if one is included.
CP2100	The IRS says a CP2100 or CP2100A means payee names and TINs on your information returns are missing or do not match its records, and you may need to start backup withholding.	The IRS says if a payee does not respond to the "B" notice, you must begin backup withholding no later than 30 business days after receiving the CP2100 or CP2100A.
CP2100A	The IRS says it issues a CP2100A when a payer filed fewer than 50 information returns with errors; the instructions match the CP2100.	The IRS says if a payee does not respond to the "B" notice, you must begin backup withholding no later than 30 business days after receiving the CP2100 or CP2100A.
CP2501	The IRS says a CP2501 means third-party income or payment information does not match your return; it is not a bill, but you must respond.	The IRS page does not give a fixed number of days; the deadline is the date printed on your notice. The IRS says to return the response form by the date listed, and you may send an extension request with your reply.
CP3219A	The IRS says a CP3219A is not a bill or audit; it notifies you of a proposed change in your tax, explains the calculation, and how you can challenge it in U.S. Tax Court.	The IRS says it cannot extend the time to respond; working with it during the 90-day period does not extend the time to file a Tax Court petition.
Letter 1058	The IRS says this notice means it has not received payment for overdue taxes, intends to seize your property or rights to property, and you must contact it immediately.	IRS Appeals says you have 30 days from receipt of an LT11 or Letter 1058 to request a Collection Due Process hearing on Form 12153 (Publication 1660 measures it from the date of the levy notice; see rights).
LT11	The IRS says this notice means it has not received payment for overdue taxes, intends to seize your property or rights to property, and you must contact it immediately.	IRS Appeals says you have 30 days from receipt of an LT11 or Letter 1058 to request a Collection Due Process hearing on Form 12153 (Publication 1660 measures it from the date of the levy notice; see rights).
LT16	The IRS says an LT16 means it is trying to collect unpaid taxes from you and/or its records show missing tax returns.	The date printed on the notice, or as soon as possible.
LT1058	The IRS says this notice means it has not received payment for overdue taxes, intends to seize your property or rights to property, and you must contact it immediately.	IRS Appeals says you have 30 days from receipt of an LT11 or Letter 1058 to request a Collection Due Process hearing on Form 12153 (Publication 1660 measures it from the date of the levy notice; see rights).

Two things the IRS says about every notice

Most notices give a response date printed on the notice itself rather than a fixed number of days, so the date on your copy is the one that counts. And when a notice gives you a right to appeal or to a hearing, the deadline for that right is strict: the pages for the LT11, CP90 and CP3219A above say how long you have.

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Sources

Every legal statement above is taken from these official texts, read on 2026-10-01.

This page is general information, not legal advice, and using it does not create an attorney-client relationship. Main AI is not a law firm. Laws change and have exceptions; the linked official text controls. For advice about your situation, contact a licensed attorney or a legal-aid office in your state.

IRS notices and letters, explained

Two things the IRS says about every notice

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