Most IRS mail is not a crisis. But it is a clock. While being on the receiving end of such a letter may not always mean an audit, it usually does mean a headache and a time sink for whoever is stepping up to handle it, whether that is you, the attorney, or your client.

This article will walk you through the eight most common IRS letters and how to handle them if you or your client should find themselves on the receiving end.

THE INITIAL TRIAGE CHECKLIST

Before jumping headfirst into responding, there are several steps to take to ensure you’re protecting both yourself as a professional and your client, whose identity and hard-earned income may be at risk. Whether the letter is addressed to your client or your firm, the first job is triage.

Step 1: Verify Legitimacy

We currently live in an age where the unfortunate truth is that most of the population suffers from regular attacks on their identity. IRS and state tax balance notices are a common method through which scammers or other ill-intentioned individuals may attempt to obtain confidential identifiers – like your name, Social Security number and address – for nefarious purposes. In fact, each year, the IRS releases a “Dirty Dozen” list of the most common scams taxpayers are likely to encounter that year. You can review it by visiting www.irs.gov/newsroom/dirty-dozen.

Adding to the confusion, some businesses operating in the tax resolution industry use tax notice lookalike mailers to market their services, particularly to individuals with recorded tax liens. These solicitations are often intentionally designed to resemble official correspondence while stopping just short of outright impersonation.

Regardless of whether the letter is sent to scam, solicit or is from the IRS, it is important to be able to identify the genuine article. Having seen thousands of IRS and state collection letters over the years, here are the three most common ways to determine whether a letter is from a taxing authority.

Verify the issuing department. Businesses that market to individuals with tax balances are not permitted to impersonate government entities. As convincing as their mailers may look, they cannot – and do not – list “Internal Revenue Service” or “Oklahoma Tax Commission” as the issuing authority.

That said, many of these letters will still reference the IRS or a state taxing authority when discussing balances, liens or collection activity. It is therefore critical to focus on who sent the letter, not simply what the letter is about.

Scammers, meanwhile, rarely bother with accuracy. It is not uncommon to see letters purportedly issued by agencies such as the “Interior Revenue Agency,” the “Department of the Interior of Revenue” or the ever-creative “Administration of the Internal Social Security Department of Revenue.” Checking the issuing department, rather than the subject matter, will nine times out of 10 tell you whether the letter is legitimate.

Check the letter number against the language of the letter. All legitimate IRS correspondence includes a specific letter or notice number, usually in the upper right corner. That number tells you what the letter is supposed to say. The IRS maintains a public index explaining each notice and its purpose.

If the letter number does not exist or the content does not match what the IRS says the notice should contain, the letter is likely not legitimate. You can verify IRS notice numbers at https://bit.ly/4tF5WzG.

Call the IRS/state directly to confirm, but do not use the phone number on the letter. If there is any doubt about a notice’s legitimacy, look up the agency’s main phone number and call it directly to confirm whether the letter was issued. Do not rely on contact information printed on the letter itself.

The IRS can be reached at 800-829-1040. The Oklahoma Tax Commission can be reached at 405-521-3160. Be aware that neither agency will discuss a taxpayer’s account without proper authorization on file. When verification is needed, the most efficient option is often to call with the taxpayer on the line or have the taxpayer call directly.

Once the notice has been identified as genuine, you can proceed with responding.

Step 2: Identify the Issue

IRS letters generally fall into one of two categories: informational or responsive. Informational letters are sent to notify taxpayers of changes, updates or activity on their accounts and typically do not require a reply. Responsive letters, by contrast, request information from the taxpayer so that the IRS can make a determination regarding the account. It is worth noting, however, that any informational IRS letter may effectively become responsive if the taxpayer disagrees with the information reported or believes the IRS has acted in error.

When a response is requested, timeliness is critical. Responsive letters will specify what information is needed and the deadline by which it must be provided. If additional time is necessary, responding by the deadline to request an extension is preferable to no response at all. However, the best practice is always to submit a complete and timely response before the stated deadline whenever possible.

Step 3: Determine Scope

Most routine IRS letters can be handled by clients themselves. In those situations, the attorney’s primary role is not substantive tax analysis but reassurance – confirming the letter is legitimate and helping the client understand what, if anything, the IRS is actually requesting. This may sound obvious, but in practice, many clients panic at the sight of IRS correspondence and fail to read the notice carefully.

Letters requesting additional documents to process a pending return, asking a taxpayer to file a missing return or providing instructions for payment generally do not require attorney involvement. Likewise, setting up a basic payment plan is often most efficiently handled directly by the client through the IRS’s online payment agreement system at https://bit.ly/41vZsY2.

For attorneys who do not regularly practice in tax matters, the safest course when a client receives a responsive IRS letter is often to recommend that the client respond themselves or consult a tax professional. The IRS does not make representation before the federal government intuitive, and notices that reference audits, appeals or tax court deadlines carry procedural risks that should not be handled casually. Those matters are best referred promptly to practitioners who regularly work in the field to avoid missed deadlines or forfeited rights.

For attorneys interested in developing a tax resolution practice, additional information on entering this area of representation is discussed later.

Step 4: Respond

Most errors in handling IRS correspondence stem from responding to the wrong issue or the wrong tax year. IRS letters are generally clear about why they were sent and what, if anything, is required in response. If a response is needed, the notice will specify the deadline, the method of response and where the information should be sent.

When responding, always include a copy of the IRS letter with the submission so the response is properly associated with the correct account and tax period. Responses may be submitted by mail or fax, depending on the instructions in the notice.

If faxing documents, retain the fax confirmation page for your records. If mailing a response, the IRS applies the mailbox rule: A response is considered timely if it is postmarked on or before the deadline. For that reason, documentation should be sent by certified mail with a return receipt requested. The IRS takes the position that, without proof of delivery, it is not responsible for responses that are lost or not received.

REPRESENTING CLIENTS BEFORE THE IRS

The IRS’s own guidance (Publication 947) defines “practice before the IRS” broadly. It includes communicating with the IRS on a taxpayer’s behalf, representing taxpayers at conferences or hearings, preparing and submitting documents for them and even providing written federal tax advice. Once an attorney crosses into representation, they are no longer simply helping a client interpret correspondence –they are operating within a regulated practice framework.

Only certain individuals are authorized to represent taxpayers before the IRS. Among those authorized are attorneys in good standing with the bar of the highest court of any U.S. state, provided they are not suspended or disbarred from practice before the IRS.

The barrier to entry, however, is lower than many attorneys expect. No formal tax training is required to begin representing taxpayers before the IRS. That said, the responsibility for accurate advice and proper representation rests entirely with the practitioner. Attorneys interested in developing competency in this area may find the IRS Volunteer Income Tax Assistance (VITA) program to be a valuable way to gain practical experience and exposure to IRS processes.

Effective representation also requires familiarity with IRS systems and procedures, including obtaining a “Centralized Authorization File” (CAF) number, setting up a Tax Pro Account and “Secure Object Repository” (SOR), accessing the “Transcript Delivery Service” (TDS) and, for those seeking to litigate, receiving admission to practice before the U.S. Tax Court.

While establishing a tax resolution practice requires an investment of time and learning, attorneys who take these steps can provide meaningful value to clients navigating IRS disputes and compliance issues.

WHEN THE IRS ASKS FOR DOCUMENTS: AUDIT AND REVENUE OFFICER REQUESTS

In addition to formal IRS notices, attorneys and their clients may receive document requests from IRS examiners or revenue officers. These requests are often issued during audits or collection investigations and should be treated differently from routine correspondence.

Audit-related document requests typically seek substantiation for items reported on a return and may be issued through formal “Information Document Requests” (Form 4564) or less formal written correspondence. Revenue officer requests, by contrast, usually arise in collection matters and focus on financial information, assets, income and the taxpayer’s ability to pay.

Unlike many informational notices, document requests in audits or collection cases are inherently responsive and substantive. The scope of the response matters. Providing incomplete information may escalate the matter, while overproducing documents can unnecessarily expand the examination or expose additional issues. As a general rule:

• Audit document requests should be answered carefully, with responses limited to the specific items requested.
• Revenue officer requests often implicate financial disclosure obligations and should not be handled casually or without understanding the downstream consequences.

Referral to a tax professional is strongly recommended when a document request:

• Is issued as part of an audit or examination
• Comes from a revenue officer rather than a centralized IRS unit
• Requests detailed financial statements, asset disclosures or business records
• Raises concerns about exposure beyond the specific tax year at issue

These requests often mark a transition from administrative processing to active enforcement, and early, strategic handling can significantly affect the outcome.

CONCLUSION

IRS correspondence is rarely the beginning of a crisis, but it is almost always the beginning of a deadline. For attorneys, the value lies not in mastering every aspect of federal tax procedure but in knowing how to triage a notice, recognize when a response is required and identify when an issue has crossed the line into one that should be handled by a tax professional.

In many cases, the most effective assistance an attorney can provide is simply helping a client slow down, read the letter carefully and respond appropriately – or directing them to the right professional before procedural rights are lost. With a basic understanding of the most common IRS letters and the risks they present, attorneys can better protect their clients from unnecessary escalation, missed deadlines and avoidable expense.

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THE EIGHT COMMON LETTERS

1) Balance Due Notices – Notice of Intent to Collect

• Letter Numbers: CP14, CP501, CP504, LT11, CP90, Letter 1058
• Notice Type(s): Informational (responsive if contested)

What it is: These notices are issued as the IRS moves through the process of notifying a taxpayer of a balance due and initiating collection activity. Depending on the stage, collection actions may include filing tax liens, wage garnishment or bank levies. Each notice identifies the amount owed, the payment deadline and the consequences of failing to respond or pay.

Why your client gets it: Common causes include a return showing tax due that was not fully paid, an additional assessment by the IRS or a payment that failed to post correctly.

How to handle it:

• Confirm the tax year and the amount due by reviewing the return and account transcript.
• If the balance is correct, pay the liability or assist the client in establishing an appropriate payment plan.
• If the balance is incorrect, follow the notice instructions and assemble supporting documentation, such as canceled checks or electronic payment confirmations proving payment was made.

When to refer out: Referral to a tax professional is advisable if either of the following applies: 1) The client disputes the validity or amount of the assessed balance, or 2) the client owes total balances exceeding $100,000 and does not intend to pay the liabilities in full within six months. In these situations, tax professionals can evaluate collection alternatives, negotiate long-term payment arrangements, pursue reductions where available or initiate appeal rights.

 

2) Proposed Changes – CP2000 Series

• Letter Numbers: CP2000, CP2000A, CP2000B, CP2000C, CP2000D and CP2000E
• Notice Type: Responsive

What it is: The CP2000 series is issued when third-party information (such as employer or financial institution reporting) does not match what the taxpayer reported on the return. The notice proposes changes that may increase, decrease or result in no change to the reported tax. The IRS expressly notes that a CP2000 is not a bill, though a response may be required.

Why your client gets it: Common causes include missing Forms 1099, mismatched basis reporting, omitted income, incorrect Schedule C gross receipts or income reported under the wrong SSN.

How to handle it:

• Review the proposed changes carefully and compare them to the return and supporting documents.
• Follow the response instructions included with the notice and submit the requested documentation by the stated deadline.
• A formal legal brief is unnecessary; a concise written explanation (generally one page or less) identifying the documents submitted and how they support the taxpayer’s position is usually sufficient.
• Even if the taxpayer agrees with the proposed changes, a response approving the adjustment is typically required to prevent further escalation.

When to refer out: Referral is appropriate when the notice involves complex basis issues, business deductions, significant dollar amounts or when the client’s position cannot be substantiated through documentation alone.

 

3) Notice of Deficiency

• Letter Number: CP3219A
• Notice Type: Responsive

What it is: CP3219A is a statutory notice of deficiency and one of the most consequential letters the IRS issues. It outlines proposed tax changes and provides a fixed deadline by which the taxpayer may petition the U.S. Tax Court. The IRS cannot extend this deadline. After it passes, the taxpayer loses the ability to contest the assessment on the merits, and any remaining relief is limited to administrative collection remedies rather than elimination of the underlying liability.

Why your client gets it: This notice typically follows an unresolved CP2000, audit findings or other proposed assessments that were not resolved at earlier stages.

How to handle it:

• If the client intends to pay the proposed liability in full, no further contest is required.
• Otherwise, this notice should be referred immediately to a tax professional admitted to practice before the U.S. Tax Court. 

When to refer out: Immediate referral is strongly advised for any client who does not intend to pay the balance in full. Missing the tax court petition deadline can permanently eliminate the taxpayer’s ability to challenge the assessment.

 

4) Math Error/Return Correction Notice

• Letter Number: CP11
• Notice Type: Informational (responsive if contested)

What it is: The IRS corrected one or more errors on the return, resulting in a change to the amount owed or refunded. 

Why your client gets it: Common triggers include arithmetic errors, mismatched credits, missing schedules or inconsistencies that the IRS is authorized to correct without initiating a full examination.

How to handle it:

• If the client agrees with the correction, pay the balance or arrange payment if applicable, and update the client’s copy of the return for records. The IRS instructs taxpayers not to send a corrected copy back.
• If the client disagrees, contact the IRS by the deadline shown in the notice and be prepared to provide supporting documentation.

When to refer out: Referral is advisable if the adjustment masks a more substantive issue – such as credit eligibility, dependency claims or documentation gaps – or if the client intends to contest the correction. Disputing a math error often escalates the matter, and submitting a well-supported response at the outset is critical to preserving appeal options.

 

5) “We Need More Information To Process Your Return”

• Letter Number: Letter 12C
• Notice Type: Responsive

What it is: Letter 12C is issued when the IRS needs additional information to process a filed return. Common requests include missing or corrected forms, verification of income, withholding or credits or confirmation of taxpayer identification information.

Why your client gets it: This notice is often triggered by missing schedules, missing forms, wage or withholding discrepancies or documentation mismatches.

How to handle it:

• The IRS generally requires the requested information to be submitted within 20 days of the notice date.
• The IRS instructs taxpayers not to file a Form 1040-X in response to the letter.
• Respond even if the taxpayer disagrees with the IRS’s position, providing clear explanations and supporting documentation.

When to refer out: These notices can often be handled in-house when the issue is limited to missing or corrected paperwork. Referral is appropriate when the client lacks required documentation and does not accept that the missing information may result in an additional tax liability.

 

6) Identity verification

• Letter Number: CP5071, 5071C, CP5071F
• Notice Type: Responsive 

What it is: The IRS issues this notice when a return has been filed using a taxpayer’s SSN or ITIN, and the IRS requires the taxpayer to verify their identity and the authenticity of the return before continuing processing.

Why your client gets it:

• The client did not file the return, indicating potential identity theft.
• The client did file the return, and the IRS requires identity verification before proceeding.

How to handle it: Have the client follow the verification instructions included in the letter.

When to refer out: Referral is rarely necessary. Identity verification is best handled directly by the taxpayer, as they are in the best position to confirm their own identity. In most cases, attorney involvement adds cost without increasing efficiency.

 

7) Refund Hold/Return Review

• Letter Number: CP05
• Notice Type: Informational

What it is: The IRS is holding the return longer to verify income, withholding, credits and/or business income and asks the taxpayer to allow up to 60 days before contacting the IRS.

Why your client gets it: Returns may be selected for review at random or flagged by IRS verification filters due to mismatches or risk indicators. The IRS specifically notes that selection for review does not mean the taxpayer made an error or acted improperly.

How to handle it:

• If the client filed the return, no action is required. The IRS advises taxpayers not to call until 60 days have passed from the notice date and only if no further correspondence has been received.
• If the client did not file the return, the notice may indicate potential identity theft. You may assist the client in completing and submitting Form 14039 (Identity Theft Affidavit).

When to refer out: Referral is generally unnecessary, as this is a notice-only letter in most cases.

 

8) Overpayment Applied/Refund Seized

• Letter Number: CP49, CP92
• Notice Type: Informational (responsive if contested)

What is it: The IRS sends this letter to notify taxpayers that an overpayment or state tax refund has been applied to offset an existing IRS balance.

Why your client gets it: When a taxpayer overpays for a given tax year, that amount is typically refunded. However, if the taxpayer has outstanding balances from prior years, the IRS may apply the overpayment – or seize a state tax refund – to reduce those liabilities.

How to handle it:

• If the client owes the balances and is already making payments, no further action is required.
• If the client was unaware of prior balances, this letter may serve as a prompt to review their account and address unresolved liabilities.
• Appealing the offset is generally unnecessary unless there is a legitimate dispute regarding the balance owed or the IRS’s authority to apply the refund.

When to refer out: If the client wishes to contest the offset, referral is advisable. These disputes can be time-consuming and often require familiarity with IRS account mechanics and internal processing errors.

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ABOUT THE AUTHOR

A dedicated tax and business attorney, Ambrielle Glass focuses her practice in high-stakes tax disputes and corporate structuring. With experience in both government and private practice, she brings a powerful combination of strategic insight and legal advocacy.