The CP45 is an IRS notice informing you that the IRS was unable to apply your overpayment to your estimated taxes for the next year as you requested on your return.

The CP3219A is an IRS Notice of Deficiency — commonly called the '90-day letter' — informing you that the IRS has determined you owe additional taxes following an audit or review. You have 90 days to petition the U.S. Tax Court to challenge the IRS's findings. Missing this deadline gives up that right permanently.

The CP2566 is an IRS notice informing you that the IRS has prepared a Substitute for Return (SFR) on your behalf because you did not file a required tax return. The IRS used income data reported by third parties to calculate your tax liability, which is typically higher than what you would owe on a properly filed return.

The CP523 is an IRS notice informing you that your installment agreement (payment plan) is at risk of being terminated due to missed or late payments. You must bring your payments current or contact the IRS immediately to prevent the agreement from defaulting.

The CP502 is the second IRS reminder notice that you have an unpaid tax balance. If you received a CP501 and did not pay or respond, the CP502 is the IRS's follow-up reminder that the balance is still due and penalties and interest are accruing.

The CP297 is an IRS notice informing you that the IRS intends to levy (seize) your property or assets to satisfy an unpaid tax debt. This notice also informs you of your right to request a Collection Due Process (CDP) hearing before the levy takes effect.

The CP210 (also called CP220 for certain entity types) is an IRS notice informing a business that the IRS has made changes to its tax return — such as a partnership, S corporation, or corporation return — and the business may now owe additional tax, have an overpayment, or have a balance due as a result.

The CP161 is an IRS notice informing a business that it has an unpaid payroll tax balance — including employment taxes, penalties, and interest. The notice demands payment and warns of potential enforcement if the balance is not resolved.

The CP92 is an IRS notice informing you that the IRS has levied your state income tax refund and applied it to your unpaid federal tax balance. The notice also informs you of your right to request a Collection Due Process Hearing

The CP91 is a final warning IRS notice informing you that the IRS intends to levy (garnish) up to 15% of your Social Security benefits to collect an unpaid tax debt. You must take action immediately to prevent the levy from taking effect.

The CP88 is an IRS notice informing you that your tax refund is being held because you have not filed a required tax return for a prior year. The IRS will not release your refund until the unfiled return is submitted and any resulting balance is resolved.

The CP81 is an urgent IRS notice informing you that the statute of limitations for claiming your tax refund for a specific year is about to expire. If you do not file your return immediately, you will permanently lose your right to receive that refund.

The CP87A is an IRS notice informing you that another taxpayer claimed a dependent with the same Social Security Number as a dependent on your tax return. The IRS is notifying both parties so the correct taxpayer can substantiate their claim and the duplicate can be removed.

The CP80 is an IRS notice informing you that the IRS has received payments or withholding credits on your behalf for a specific tax year, but has not received your tax return for that year. If you were required to file, you should file immediately to avoid losing those credits.

The CP72 is an IRS notice informing you that the IRS believes your tax return contains a frivolous position — a tax argument that has no legal basis under U.S. tax law. The IRS may impose a $5,000 civil penalty if you do not correct or explain your position.

The CP71C is an annual IRS reminder notice informing you that you still have an outstanding tax balance that has not been resolved. The notice also warns that the IRS may offset any federal payments you receive — including Social Security — against your outstanding balance.

The CP60 is an IRS notice informing you that a payment that was previously applied to your tax account has been reversed or removed due to an error. As a result, you now have a balance due for the amount of the removed payment.

The CP54B is an IRS notice informing you that the name or Social Security Number (SSN) on your tax return does not match the information the IRS has on file. You need to respond with documentation to verify your identity and correct the discrepancy before your return can be processed.

The CP42 is an IRS notice informing you that the amount of your tax refund has been reduced because it was applied to your spouse's past-due federal or state tax debt. If you believe you should not be responsible for your spouse's debt, you may qualify for Injured Spouse relief.

The CP53 is an IRS notice informing you that your tax refund cannot be delivered by direct deposit and will instead be sent to you as a paper check in the mail. No action is required — just watch for your check.

The CP32 is an IRS notice informing you that a replacement refund check has been issued. This typically follows a prior refund check that was lost, never received, or returned to the IRS.

The CP31 is an IRS notice informing you that your refund check was returned to the IRS because it was undeliverable. You need to update your address so the IRS can reissue your refund.

The CP40 is an IRS notice informing you that your overdue tax account has been assigned to a private collection agency. The IRS works with authorized private collectors to recover certain unpaid taxes. You still have the same rights and options as if the IRS were collecting directly.

The CP24 is an IRS notice informing you that the IRS found a discrepancy between the estimated tax payments on your return and those posted to your account — in your favor. The IRS has determined you have a credit and will either issue a refund or apply it to other taxes owed.

The CP23 is an IRS notice informing you that the IRS found a discrepancy between the estimated tax payments you reported on your return and the payments actually posted to your IRS account, resulting in a balance due. You have the right to pay, dispute, or set up a payment plan.

The CP25 is an IRS notice informing you that the IRS found a discrepancy between the estimated tax payments on your return and those on file — but the adjustment results in a zero balance. You neither owe money nor are receiving a refund as a result of this change.

The CP05 is an IRS notice informing you that your tax return has been selected for review and that your refund is being held while the IRS verifies your income, withholding, tax credits, or business income. No action is typically required, but understanding the process is important.

The CP75 is an IRS audit notice requesting documentation to verify credits you claimed on your tax return, most commonly the Earned Income Tax Credit (EITC). You must respond with supporting documents to receive the credit.

The CP2000 is the IRS's notice that income or deductions on your tax return don't match what was reported by third parties like employers or financial institutions. It is not an audit, but it does propose additional taxes you may owe and requires a response.

The CP21A informs you that the IRS has made changes to your tax return, typically based on an amended return you filed, and that a balance is now owed as a result of those changes.

The CP30 notifies you that the IRS has charged you an Estimated Tax Penalty because you did not pay enough in estimated taxes throughout the year. This is common for self-employed individuals, freelancers, and investors who owe tax beyond what was withheld.

The CP01A provides your annual IRS Identity Protection PIN (IP PIN), a six-digit number you must use when filing your federal tax return to protect your identity and prevent fraudulent returns from being filed in your name. A new number is issued each year.

The CP49 notifies you that the IRS has applied your tax refund to an outstanding tax balance from a prior year. If your refund was larger than the balance owed, the notice will show any remaining refund amount being returned to you.

The CP521 is a reminder that you have an active IRS installment agreement and that a payment is due. It shows your current balance, your scheduled payment amount, and your payment due date.

The CP162 is an IRS penalty notice issued to partnerships, S-Corporations, and other pass-through entities for filing their tax return late. The penalty is assessed per partner or shareholder, per month, and can add up quickly.

The CP22A notifies you that the IRS has made changes to your tax return, often based on information you provided, and that as a result you now owe additional taxes. It is a formal bill for the adjusted balance.

The CP12 is an IRS notice informing you that they made changes to your tax return due to a math or calculation error, and that as a result, you are owed a larger refund than originally calculated, or your balance due has been reduced.

The CP2501 is an IRS notice alerting you to a discrepancy between the income reported on your tax return and what third parties reported to the IRS. Unlike the CP2000, this is an early inquiry, not yet a formal bill, giving you an opportunity to explain or correct the discrepancy.

The CP90 is the IRS's Final Notice of Intent to Levy and Notice of Your Right to a Hearing. This is one of the most serious notices the IRS sends, it means levy action is imminent and you have limited time to protect your assets.

The CP59 is the IRS's first notice informing you that they have no record of you filing a required tax return. It requests that you either file the missing return immediately or explain why you were not required to file.

The CP504 is one of the most serious IRS balance due notices. It is a Notice of Intent to Levy, meaning the IRS is warning you they are about to seize your assets, including your state tax refund, bank accounts, and wages, if you do not pay or respond immediately.

The CP503 is the IRS's second reminder notice that you have an unpaid tax balance. It signals that the IRS is escalating collection efforts and that serious enforcement, including levies and wage garnishment, is approaching if you do not respond.

The CP501 is the IRS's first reminder that you have an unpaid tax balance from a previous notice. It means the IRS has not received payment or a response and is beginning to escalate collection efforts.

The CP11 is an IRS notice informing you that they made changes to your tax return due to a math or calculation error, and that you now owe additional taxes as a result. You have the right to agree with the changes or dispute them if you believe the IRS is wrong.

The CP14 is the IRS's first official notice that you owe unpaid taxes. It outlines the exact amount due, including any penalties and interest, and requests payment. Ignoring it triggers a collection escalation that can lead to liens and levies.