Each type involves different procedures, different IRS personnel, different scope, and different stakes. Identifying which type of audit you are facing is the first defensive step in any examination.

This article walks through the three audit types from the inside — how they are conducted, who staffs them, what issues each tends to involve, and what each one signals about the IRS’s interest in the case.

The perspective is informed by Kugelman Law attorney Otto Bosch, who served as a Revenue Agent in the IRS Global High Wealth Group within the Large Business and International (LB&I) Division before joining the firm in February 2026. For broader background on how Revenue Agents operate, see our companion articles on what an IRS Revenue Agent does and inside the IRS audit playbook.

Why the Type of IRS Audit Matters

The type of audit determines almost everything else about the examination. Correspondence audits are conducted through the mail, generally by tax examiners working from IRS Service Centers, and typically focus on narrow, document-driven issues.

Office audits are conducted in person at IRS offices, generally by Tax Compliance Officers, and cover a broader scope.

Field audits are conducted at the taxpayer’s place of business or representative’s office, generally by Revenue Agents, and are the most substantive type — often involving multi-year examinations of complex returns.

The differences matter for three reasons:

Procedurally, the workflows, timelines, and document expectations differ significantly across types.

Substantively, the issues likely to arise differ based on the audit type. A correspondence audit is rarely the right vehicle for a complex partnership examination. A field audit is rarely opened for a missing 1099.

Strategically, the level and type of representation appropriate to each varies. A correspondence audit may be handled directly by the taxpayer or the preparer. A field audit conducted by an LB&I Revenue Agent almost always requires experienced controversy counsel.

Correspondence Audits

A correspondence audit is conducted entirely through written communication, typically initiated by a letter from the IRS — often a CP2000 notice or a similar document — that identifies a specific discrepancy and requests substantiation or explanation.

Who conducts them. Correspondence audits are generally handled by tax examiners at IRS Service Centers, working through the Automated Underreporter (AUR) program or similar automated functions. The taxpayer typically does not have a single named agent to communicate with. Replies go to a Service Center, where a different reviewer may process each response.

Typical issues. Correspondence audits focus on narrow, well-defined issues that can be resolved through document production:

• Information matching mismatches (a 1099 the IRS received but does not match the return)
• Missing or incorrect Social Security numbers for dependents
• Earned Income Tax Credit eligibility verification
• Education credit substantiation
• Itemized deduction verification on a single category (charitable contributions, medical expenses)
• Simple math errors or credit calculation questions

Scope. Limited and pre-defined. The IRS letter identifies what is being examined and (usually) limits the inquiry to that issue.

Risk profile. Correspondence audits are not low-stakes by default — many produce significant adjustments — but the risk of unbounded expansion is lower than with office or field audits. The greater risk is mishandling: failing to respond by the deadline, responding incompletely, or responding in a way that creates new issues.

When to engage counsel. Most correspondence audits do not require attorney involvement. They can typically be handled by the taxpayer directly or by the return preparer. Counsel is appropriate where the dollar amounts are significant, where the underlying facts touch on potential criminal exposure, or where the correspondence audit appears to be a precursor to a broader examination.

Office Audits

An office audit is conducted in person at an IRS office, typically as a single appointment lasting several hours to a full day. The taxpayer (or representative) brings requested documents to the appointment and meets with the examiner to address specific issues.

Who conducts them. Office audits are generally conducted by Tax Compliance Officers (TCOs), though Revenue Agents may handle some office examinations. Unlike correspondence audits, the taxpayer has a single named examiner with whom communications occur.

Typical issues. Office audits address moderately complex issues that benefit from in-person review:

• Schedule C examinations of self-employed taxpayers
• Schedule E rental property issues
• More complex itemized deduction questions (including travel and entertainment substantiation)
• Multi-year individual return issues
• Credit eligibility questions requiring document review

Scope. Broader than correspondence audits, narrower than field audits. The IRS will typically issue an Information Document Request before the appointment listing the specific documents and issues to be examined.

Risk profile. Office audits carry meaningful risk of expansion. Issues identified during the appointment can lead to follow-up examinations, related-return pickups, or escalation to a field audit if complexity warrants. Statements made during the appointment become part of the examination record.

When to engage counsel. Office audits frequently benefit from representation, particularly where the issues are substantive, the dollar amounts are meaningful, or the taxpayer is uncomfortable with the prospect of in-person examination by a trained IRS employee. CPAs and EAs can represent in office audits; attorneys add the privilege protection and litigation backstop that matter in more complex cases.

Field Audits

A field audit is the most comprehensive type of IRS examination. It is conducted in person at the taxpayer’s place of business, the representative’s office, or another location convenient to the examination, and typically extends over months — sometimes years — rather than days.

Who conducts them. Field audits are conducted by Revenue Agents. The division and specialization of the Revenue Agent reflects the type of case:

• Small Business / Self-Employed (SB/SE) Revenue Agents handle most individual and small-business field audits
• Large Business and International (LB&I) Revenue Agents handle complex corporate, partnership, and high-net-worth examinations
• The Global High Wealth Group within LB&I handles the most specialized examinations of the wealthiest U.S. taxpayers, using an enterprise audit approach that considers entire structures of related entities and transactions

Typical issues. Field audits address the most complex tax issues:

• Multi-year individual and business return examinations
• Partnership and S-corporation issues, including basis disputes and related-party transactions
• High-net-worth taxpayer examinations involving multiple entities and structures
• Cryptocurrency examinations of active traders, NFT participants, and DeFi users — covered in our article on inside an IRS cryptocurrency audit
• Foreign account and offshore disclosure matters
• Allegations of fraud or willful conduct
• Industry-specific examinations conducted as part of LB&I campaigns

Scope. Field audits typically cover one or more complete tax years, with the agent reviewing the return in its entirety rather than focusing on a single issue. Multiple Information Document Requests are issued over the course of the examination, with the scope evolving as issues develop.

Risk profile. Field audits represent the IRS’s most resource-intensive examination type. By the time the IRS opens a field audit, the agency has decided the case is worth investing significant time and analytical resources in. Cases conducted under the Global High Wealth Group’s enterprise approach use multiple specialists and consider the full web of related entities and transactions.

When to engage counsel. Field audits — particularly those conducted by LB&I or the Global High Wealth Group — almost always benefit from experienced tax controversy counsel. The combination of substantive complexity, multi-year scope, specialized examiner training, and significant dollar exposure makes attorney representation the appropriate default. Where there is any potential for criminal exposure or aggressive penalty positions, attorney representation is essential. We covered this calculus in detail in our article on tax attorney vs CPA for IRS audit defense.

Where the Three Types Overlap and Where They Don’t

A few important nuances apply across all three audit types:

The taxpayer’s legal rights are the same in each type. The right to representation, the right to obtain a copy of the audit report, the right to appeal proposed adjustments, the right to challenge a notice of deficiency in U.S. Tax Court — these rights do not vary based on whether the audit is conducted by correspondence, in an office, or in the field.

The substantiation rules are the same. Section 274(d) substantiation requirements for travel and entertainment expenses, basis documentation requirements, charitable contribution substantiation under Section 170 — these requirements apply identically across audit types. The differences are in how and how rigorously they are tested.

Audits can convert from one type to another. A correspondence audit that uncovers complexity can be escalated to an office or field audit. An office audit that surfaces issues outside the original scope can become a field audit. A field audit that develops potential criminal exposure can be referred to IRS Criminal Investigation. Recognizing the signals that an audit is converting type is one of the most valuable defensive insights — and it is precisely the kind of inside-the-IRS perspective that comes from prior IRS service.

How the Type of Audit Shapes Defense Strategy

Defense strategy in any IRS examination begins with correctly identifying the type of audit, the IRS division conducting it, and the specific examiner’s training and authority. From there, several principles apply:

For correspondence audits, the defense priority is responsiveness and accurate document production. Missing the deadline, providing incomplete responses, or volunteering information not requested are the most common errors. Where the issue can be cleanly substantiated, a focused response often produces a no-change closing.

For office audits, the defense priority is preparation. The single in-person appointment is where the audit’s record is largely built. Pre-appointment review of documents, anticipation of likely questions, and preparation of organized exhibits typically determine the outcome. As discussed in our article on how to respond to an IRS IDR, the appointment is not the time for improvisation.

For field audits, the defense priority is methodology. Multi-year, multi-issue examinations require sustained, organized, document-driven defense across months or years. The record built during the field audit is the record that follows the case to Appeals, to U.S. Tax Court, and through any subsequent litigation. This is the type of audit where the inside-the-IRS perspective of a former Revenue Agent — the focus of our article on why a former IRS revenue agent attorney changes audit defense — most directly changes outcomes.

What Each Type Tells You About the IRS’s Interest in the Case

The type of audit the IRS opens carries information about the agency’s view of the case. A correspondence audit signals that the IRS has identified a specific, narrow issue and believes it can be resolved through document production. An office audit signals that the IRS sees enough complexity to warrant in-person review but not enough to justify field resources. A field audit — particularly one conducted by LB&I or the Global High Wealth Group — signals that the IRS believes the case is worth investing significant resources in.

Conversely, the absence of certain audit types can also be informative. A taxpayer whose return contains issues that would normally warrant a field audit, but who receives only a correspondence audit, may be facing a case where the IRS does not yet appreciate the scope. That dynamic creates specific defensive considerations — and is one of the reasons experienced controversy counsel reads each audit’s type, scope, and selection signals carefully before deciding how to respond.

How Kugelman Law Handles Each Audit Type

Kugelman Law’s audit defense practice is calibrated to the type of audit and the complexity of the underlying issues. For correspondence audits with significant exposure or potential complexity, the firm provides focused review and response strategy. For office audits, the firm provides full pre-appointment preparation, representation at the examination, and follow-through. For field audits — particularly those conducted by LB&I or the Global High Wealth Group — the firm provides the sustained, methodology-driven defense that complex multi-year examinations require.

Founder Alex Kugelman brings nearly two decades of federal tax controversy experience, including litigation in U.S. Tax Court and U.S. District Court. Otto Bosch brings the inside-the-IRS perspective from his time as a Revenue Agent in the IRS Global High Wealth Group within LB&I — including direct experience with the examination types and divisional procedures that govern most substantive audits.

Representative outcomes from the firm’s audit defense practice include a $365,000 tax debt reduced to a zero-dollar liability, a multi-year audit and non-filing matter resolved with minimal payment, and ten years of unfiled returns brought into compliance with a successful outcome. Results depend on specific facts. Past results do not guarantee future outcomes.

Frequently Asked Questions

How do I know what type of IRS audit I am facing?

The initial IRS letter identifies the type of audit. A letter asking for documents to be mailed in is a correspondence audit. A letter scheduling an in-person appointment at an IRS office is an office audit. A letter from a Revenue Agent proposing to meet at your place of business or your representative’s office is a field audit. The letter will also identify the examiner’s title (tax examiner, Tax Compliance Officer, Revenue Agent) and the IRS division conducting the examination.

Is a correspondence audit less serious than a field audit?

Generally yes — but not always. Correspondence audits typically involve narrower issues and smaller dollar amounts, but they can produce significant adjustments and can escalate to broader examinations if the response surfaces complexity. The right approach is to take any IRS audit seriously regardless of type.

Can an office audit turn into a field audit?

Yes. Where the issues identified during an office audit prove more complex than expected, or where the scope expands to multiple years or related entities, the IRS can escalate the examination to a field audit. This is one of the reasons preparation for an office audit appointment matters — what surfaces at the appointment shapes whether the case stays narrow or expands.

Do I have to let an IRS Revenue Agent into my home or business?

You generally have the right to conduct an audit at your representative’s office rather than at your home or place of business, particularly when you are represented by an attorney, CPA, or EA. Revenue Agents typically accommodate reasonable location requests where the relevant records can be made available.

Who decides what type of audit will be conducted?

The IRS decides, based on the issues identified at selection, the complexity of the return, and the dollar amounts at stake. Taxpayers generally do not have the ability to elect one type over another, though the choice of representative and the location of the audit can be negotiated in field examinations.

Speak With Kugelman Law

If you have received an IRS audit notice of any type — correspondence, office, or field — schedule a paid privileged consultation with Kugelman Law. Call (415) 968-1780 or visit our contact page. All consultations are fully protected by attorney-client privilege.

About the Author

Alex Kugelman is the founder and managing attorney of Kugelman Law, a boutique tax controversy and cryptocurrency tax firm serving California and clients nationwide. With nearly two decades of federal tax controversy experience — including litigation in the U.S. Tax Court and U.S. District Court — Alex represents individuals and businesses in their most consequential disputes with the IRS and the California Franchise Tax Board. He is a member of the State Bar of California (No. 255463), admitted to the Bar of the U.S. Supreme Court, and served as San Francisco Chair of the Federal Bar Association’s Tax Division in 2018. He is also a member of the Marin County Assessment Appeals Board and a nationally recognized cryptocurrency tax attorney featured on the Bitcoin.tax podcast and The Mark Milton Show. Read Alex’s full bio.