Did you know each letter from the IRS is labeled with a form number that indicates it’s purpose? Here are some common ones:

CP01 The IRS verified your claim of identity theft and will monitor your account.
CP01H The IRS received a tax return with a social security number that belongs to a dead person.
CP02H Money is due on an amended return based on a grant received due to Hurricane Katrina, Rita, or Wilma.
CP03C You received the First-Time Homebuyer Credit for a house you purchased.
CP04 You may be eligible for tax deferment because either you or a spouse served in a combat zone, a qualified contingency operation, or a hazardous duty station during the tax year specified on your notice.
CP08 You may be entitled to additional money due to the Additional Child Tax Credit.
CP10 Your tax return changed due to a miscalculation, and the refund you wanted to apply to an estimated tax payment has changed.
CP10A Your tax return changed due to a miscalculation of the Earned Income Credit, and the refund you wanted to apply to an estimated tax payment has changed.
CP11 You owe money because the IRS amended your return due to a miscalculation.
CP11A Your tax return changed due to a miscalculation of the Earned Income Credit, and the refund you wanted to apply to an estimated tax payment also changed.
CP11M Your tax return changed due to a miscalculation of the Making Work Pay and Government Retiree Credit, and the refund you wanted to apply to an estimated tax payment has changed.
CP12 You are due a bigger refund because the IRS corrected one or more mistakes on your tax return.
CP12A The IRS made changes to correct the Earned Income Credit (EIC) claimed on your tax return.
CP12E or CP12F The IRS corrected a miscalculation on your return.
CP12M The IRS made changes to the computation of the Making Work Pay and/or Government Retiree Credits on your return.
CP12R The IRS made changes to the computation of the Rebate Recovery Credit on your return.
CP13 The IRS made changes to your return due to a miscalculation. There is no refund or amount due. Your balance is zero.
CP13A The IRS made changes to your return due to a miscalculation of the Earned Income Credit. There is no refund or amount due. Your balance is zero.
CP13M The IRS made changes to your return due to a miscalculation of the Making Work Pay credit or the Government Retiree Credit. There is no refund or amount due. Your balance is zero.
CP13R The IRS made changes to your return due to a miscalculation of the Recovery Rebate Credit. There is no refund or amount due. Your balance is zero.
CP14 You owe money on unpaid taxes.
CP16 The IRS made changes to your return due to a miscalculation. The refund you were due was applied to other tax debts.
CP21A You owe money due to the changes you requested that the IRS make on your tax returns.
CP21B You are due a refund due to the changes you requested that the IRS make on your tax returns. The money should arrive within 2 to 3 weeks.
CP21C The IRS made the requested changes to your tax return. You will not receive a refund, and there is no tax due. Your balance is zero.
CP21E As a result of your recent audit, the IRS made changes to your tax return, and you owe money as a result of those changes.
CP21I The IRS made changes to your tax return relating to the Individual Retirement Arrangement (IRA) taxes. You owe money due to the changes.
CP22A The IRS made the changes you requested, and you owe money as a result.
CP22E As a result of your recent audit, the IRS changed your tax return, and you now owe money.
CP22I The IRS made changes to your tax return relating to the Individual Retirement Arrangement (IRA) taxes. You owe money due to the changes.
CP23 The IRS changed your return because there was a difference between the amount of estimated tax payments listed on your tax return and the amount actually posted to your account. You owe taxes due to these changes.
CP24 The IRS changed your return because there was a difference between the amount of estimated tax payments listed on your tax return and the amount actually posted to your account. This resulted in an overpayment of estimated taxes.
CP24E The IRS changed your return because there was a difference between the amount of estimated tax payments listed on your tax return and the amount actually posted to your account. This resulted in an overpayment of estimated taxes.
CP25 The IRS changed your return because there was a difference between the amount of estimated tax payments listed on your tax return and the amount actually posted to your account. You are not due a refund, nor do you owe any money. Your balance is zero.
CP31 You need to update your address because your refund check was returned to the IRS.
CP45 The IRS was unable to apply your overpayment to your estimated tax as you requested.
CP49 The IRS used all or part of your refund to pay a tax debt.
CP53 Your refund check will be sent by mail because the IRS can’t provide your refund through direct deposit.
CP57 The bank declined your payment, so the IRS was unable to draft funds from your bank account.
CP71 A reminder of the amount you owe in tax, penalty, and interest.
CP71A A reminder of the amount you owe in tax, penalty, and interest.
CP71C A reminder of the amount you owe in tax, penalty, and interest.
CP71D A reminder of the amount you owe in tax, penalty, and interest.
CP88 The IRS is holding your refund because you haven’t filed one or more tax returns, and it believes you will owe tax.
CP90 The IRS is notifying you of its intent to levy certain assets for unpaid taxes. You have the right to dispute the levy in a Collection Due Process hearing.
CP91 The IRS will levy up to 15% of your social security benefits for unpaid taxes.
CP120 The IRS needs documentation of your tax-exempt status.
CP120A Your organization’s tax-exempt status has been revoked because it failed to file a Form 990 series return for three consecutive years.
CP130 You may no longer need to pay the Alternative Minimum Tax (AMT) because your tax return filing requirements changed.
CP152 The IRS received your return.
CP153 The IRS will send your refund by mail because your direct deposit did not go through.
CP161 You have an unpaid balance due to the IRS.
CP166 Your monthly payment to the IRS did not go through due to insufficient funds in your bank account.
CP178 You may no longer owe excise tax because your tax return filing requirements changed.
CP231 You need to update your address because your refund was returned to the IRS.
CP259 You did not file the business tax return identified in the notice.
CP259A You should have filed these forms but did not – Form 990/990-EZ, Return of Organization Exempt From Income Tax, or Form 990-N (e-Postcard).
CP259B The IRS requires you to file these forms but did not – Form 990-PF, Return of Private Foundation or Section 4947(a)(1) Nonexempt Charitable Trust Treated as a Private Foundation.
CP259C The IRS believes that you are a private foundation, but did not file the required Form 990-PF, Return of Private Foundation or Section 4947(a)(1) Nonexempt Charitable Trust Treated as a Private Foundation.
CP259D You must file this form, but you did not – Form 990-T, Exempt Organization Business Income Tax Return.
CP259E You should have filed this form, but you did not – Form 990-N (e-Postcard) or Form 990/990-EZ, Return of Organization Exempt From Income Tax.
CP259F The IRS requires you to file this form but did not – Form 5227, Split-Interest Trust Information Return.
CP259G The IRS requires you to file this form, but you didn’t – Form 1120-POL, U.S. Income Tax Return for Certain Political Organizations.
CP259H As a tax-exempt political organization, you must file this form, but you did not – Form 990/990-EZ, Return of Organization Exempt From Income Tax.
CP276A You submitted your tax liability schedule incorrectly. The IRS typically charges a Federal Tax Deposit (FTD) penalty for this but did not this time.
CP276B The IRS did not receive the correct amount of tax deposits. It normally charges a Federal Tax Deposit (FTD) penalty but did not this time.
CP297 The IRS is notifying you of its intent to levy certain assets for unpaid taxes. You have the right to dispute the levy at a Collection Due Process hearing.
CP297A The IRS has levied your assets for unpaid taxes. You have the right to dispute the levy at a Collection Due Process hearing.
CP298 The IRS notifying you of its intent to levy up to 15% of your social security benefits for unpaid taxes.
CP501 You have a balance due on one of your tax accounts.
CP503 You have an unpaid balance on one of your accounts, and the IRS has not heard from you.
CP504 You have an unpaid amount due on your account. If you do not pay immediately, the IRS will levy your state income tax refund to apply it to the amount you owe.
CP504B You have an unpaid amount due on your account. If you do not pay immediately, the IRS will levy certain property or rights to property to apply it to the amount you owe.
CP521 A reminder that you have an installment agreement payment due.
CP523 You have defaulted on your payment agreement. Therefore the IRS is terminating the agreement and will levy your assets.
CP2000 The income or payment information on file doesn’t match your tax return. The discrepancy may result in an increase or decrease in your tax due.
CP3219A The IRS has received information that is different from what you reported on your tax return. This may result in an increase or decrease in your tax.
CP3219N The IRS didn’t receive your tax return, so it calculated your return based on the information received from employers, financial institutions, and others. If you want to challenge the proposed tax, you have 90 days from the date of this notice. If you are outside the country, you have 150 days.
Letter 0012C The IRS needs additional information to process your tax return.
Letter 0484C The IRS wants a completed Financial Statement so it can determine your ability to pay.
Letter 0525 Updates you on proposed changes after an IRS examination. Any changes are explained and details the refund due or taxes owed.
Letter 531 IRS Notice of Deficiency. The information the IRS received about you was different from what you reported on your return.
Letter 0668D(LP 68) The IRS released their levy.
Letter 0549C Your tax bill was paid.
Letter 0668D(LP 68) The IRS released their levy.
Letter 0681C The IRS accepted your payment proposal. However, this is not a formal Installment Agreement.
Letter 0757C You did not adhere to the terms of your Installment Agreement.
Letter LT 11 The IRS plans to seize your property or rights to property.
Letter 1058 The IRS has not received your payment. It plans to seize your property or rights to property.
Letter 1615 (LT 18) You must respond to the IRS within 10 days of this notice regarding past due tax returns.
Letter 1731 (LP 64) The IRS is requesting your assistance in locating someone. You need to provide their address and work information.
Letter 1737 (LT 27) Complete and sign Form 433F, Collection Information Statement.
Letter 1961C Your application for a Direct Debit Installment Agreement was declined. It explains why and what you need to do to qualify.
Letter 1962C Your application for a Direct Debit Installment Agreement has been approved. It explains the fees and how to qualify for a Low Income Fee Reduction.
Letter 2050 (LT 16) The IRS is trying to collect unpaid taxes from you from returns that have been filed or from returns that have not been filed.
Letter 2257C The IRS is providing the payoff amount that you requested.
Letter 226-J An IRS letter to large employers notifying them that they may be liable for an Employer Shared Responsibility Payment (ESRP).
Letter 2271C A request for an Installment Agreement has been approved. It explains the fees and how to qualify for a Low Income Fee Reduction. The letter may also request missing information.
Letter 2272C An IRS letter explaining why your request to pay the balance due in installments was declined.
Letter 2273C A confirmation letter of your request to pay the balance due in installments. It contained the amount to pay, fees charged, and where to send payment. Instructions on how to apply for the Low Income Fee Reduction included.
Letter 2318C A response to a request to pay taxes due to payroll deductions. It also explains the fees that are charged.
Letter 2357C The IRS is admitting that it did not send you the balance due notices that it should have.
Letter 2603C The IRS accepted your installment agreement. The IRS will file a Notice of Federal Tax Lien on your personal property.
Letter 2604C The IRS has accepted your request for installment payments. This IRS letter provides the monthly payment, the address where to send it, and the fees charged. The letter also provides instructions on how to apply for the Low Income Fee Reduction.
Letter 2761C The IRS is requesting your combat zone service dates to ensure that it provides you with the special provisions and protection of the combat zone deferment. Copies of military orders or other documentation to support your time served may be requested. Civilians working in support of the Armed Forces may be required to provide a Letter of Authorization or a letter from their employer.
Letter 2789C An annual reminder notice, as required by law, of the balance due to the IRS. It explains that penalties and interest continue to accrue until the balance is fully paid.
Letter 2840C Confirms your Installment Agreement request and includes the payment amount and due date. This IRS letter explains the fees charged for paying monthly and explains how to apply for the Low Income Fee Reduction (if you qualify).
Letter 3030C Provides an explanation of the tax, penalty, and interest still due on your account.
Letter 3127C A confirmation of your request to make a change to your Installment Agreement. This IRS letter explains the fees for the change. Changes can be to the payment amount or due date, or it can include additional liabilities.
Letter 3174 A reminder of taxes due after the IRS has sent a Notice of Intent to Levy.
Letter 3217C The IRS has accepted your request to pay the balance in installments. This IRS letter provides your payment amount, the due date, and fees charged. The letter also provides instructions on applying for the Low Income Fee Reduction (if you qualify).
Letter 3228 (LT 39) A request to pay the balance due within 10 days using the envelope provided.
Letter 3500 The IRS has received your documents, and it needs additional time to review them.
Letter 3572 Your Federal Income Tax Return has been selected for examination. The IRS auditor requests that you call to schedule an audit appointment.
Letter 4883C The IRS received your federal income tax return but needs more information to verify your identity in order to process your tax return accurately.
Letter 4903 (LT 26) You must file your tax returns immediately. The IRS has previously contacted you, but it did not receive a response.
Letter LP 47 The IRS is trying to locate the person identified in the letter and is requesting that you provide their new address.
Letter LP 59 The IRS has not received a response to the notice of levy it previously sent.
Audit Letter 2205 The IRS manages audits either by mail or through an in-person interview to review your records. The interview may be at an IRS office (office audit) or the taxpayer’s home, place of business, or accountant’s office (field audit).
Letter 915 You recently underwent an audit, and the IRS informs you that you now owe taxes.

This list excludes letters not issued in a language other than English.