Overview
The Internal Revenue Service (IRS) is a large federal agency with several operating divisions and support offices that together administer the nation’s tax laws. The structure is designed to match staff expertise with taxpayer type and tax issue complexity, so individuals, small businesses, large corporations, and tax-exempt organizations receive appropriate, specialized attention. For the most current organizational details and contacts, consult the IRS “About” pages on IRS.gov. (Source: IRS.gov — About the IRS: https://www.irs.gov/about-irs)
In practice, directing your inquiry to the correct division shortens response times and reduces misrouted correspondence. As a CPA with 15+ years assisting clients through audits, collections, and appeals, I’ve seen how a properly targeted contact can materially affect outcomes.
Key leadership and functional roles
- Commissioner of Internal Revenue: The agency’s chief executive, responsible for overall administration and execution of federal tax laws. The Commissioner is a Senate-confirmed position that oversees the IRS’s operating divisions and staff offices.
- Deputy Commissioners and Assistant Commissioners: Senior leaders who manage broad functional areas such as operations, enforcement, and taxpayer services.
- Chief Counsel: The IRS’s in-house legal office that issues legal advice, drafts regulations, and represents the IRS in litigation.
- Support functions: Information Technology (IT/modernization), Human Capital, Finance, Research, and Policy groups that enable core operations.
Main operating divisions and who they serve
The IRS organizes most front-line work into taxpayer-focused operating divisions. These are the groups taxpayers and practitioners most often need to understand.
Wage & Investment (W&I)
- Primary taxpayers: Individuals, retirement filers, and many very small businesses.
- Typical work: Processing Forms 1040 and 1040-SR, answering individual account inquiries, issuing notices for individual return adjustments, conducting examinations for individual taxpayers, and handling many collection actions for personal tax liabilities.
- Practitioner tip: If you received a CP/letter for an individual return or need help with filing/filing status, start with W&I. Many resolution paths (installment agreements, identity protection, refund offsets) are administered here.
Small Business/Self-Employed (SB/SE)
- Primary taxpayers: Small businesses (commonly those with assets generally under $10 million), self-employed individuals, sole proprietors, S corporations and partnerships within the SB/SE assignment rules.
- Typical work: Employment tax issues, business return examinations, payroll tax compliance, and collections for small-business liabilities.
- Note on thresholds: Asset thresholds and assignment rules can change; treat the $10 million marker as a general guideline rather than a fixed statutory cutoff.
Large Business & International (LB&I)
- Primary taxpayers: Large corporations, partnerships, and complex entities—often those with assets or revenues above LB&I assignment limits, and companies with significant international operations.
- Typical work: Complex audits, transfer pricing analysis, international tax compliance, treaty issues, and large-scale compliance projects.
- Practitioner tip: LB&I audits are document- and resource-intensive. Large taxpayers often use coordinated case teams and pre-audit conferences.
Tax Exempt & Government Entities (TE/GE)
- Primary taxpayers: Tax-exempt organizations (501(c) organizations), private foundations, retirement and pension plans, and federal/state/local government entities.
- Typical work: Determining tax-exempt status, reviewing Form 990 filings, monitoring private foundation excise taxes, and ensuring compliance with nonprofit rules.
- Practical note: TE/GE has both application and compliance teams—contact TE/GE for exemption applications and any compliance reviews.
Independent and support units that affect taxpayers
Taxpayer Advocate Service (TAS)
- Role: TAS is an independent organization within the IRS that helps taxpayers who are experiencing economic harm or who cannot resolve problems through normal IRS channels. TAS can issue Taxpayer Assistance Orders and works to protect taxpayer rights.
- When to use: If IRS actions (or inaction) cause financial hardship, prolonged delay, or a systemic error affecting you, TAS offers an independent escalation path.
- Internal link: See our detailed guide to the Taxpayer Advocate Service (TAS) for when and how to request assistance.
- External reference: TAS’s role and authority are described on IRS and TAS pages (see IRS “About the IRS”).
Office of Appeals
- Role: The Appeals office provides an independent, administrative review of disputed IRS determinations without going to court. Appeals officers are separate from the examining or collection teams.
- When to use: File an administrative appeal if you disagree with an examination or collection decision but want to avoid litigation.
- Internal link: For step-by-step instructions and strategy, read our article on How to File an Administrative Appeal with the IRS Office of Appeals.
Criminal Investigation (CI)
- Role: CI is the IRS’s law enforcement branch. It investigates criminal tax violations, money laundering, and related offenses. CI operates separately from civil tax functions; being under CI investigation is materially different from a civil audit.
- Practical note: If you receive a CI contact (often served in person), engage counsel immediately—criminal matters raise different stakes than civil disputes.
Chief Counsel
- Role: Provides legal opinions, defends the IRS in litigation, and develops regulations. Chief Counsel involvement is typical in complex or precedent-setting matters.
IT, Modernization, and Human Capital
- Role: These support groups manage the IRS’s technology platforms, modernization initiatives, and employee training. Modernization work affects e-file systems, online accounts, and taxpayer-facing services.
How cases are assigned and why it matters
The IRS assigns cases based on the taxpayer type, issue complexity, monetary thresholds, and internal case inventory rules. That means two taxpayers with the same issue could be handled by different divisions if their business size or filing history differs. Always confirm the office handling your case using the contact information on the IRS notice or your online account.
How to navigate the structure for faster resolution
- Read the notice carefully: Contact details and the proper office are typically printed on the notice or letter.
- Use IRS online tools first: Many account problems, balances, and transcript requests are resolved faster online.
- Escalate properly: If standard contacts fail or the issue causes hardship, contact the Taxpayer Advocate Service or submit an appeal (see link above).
- Keep records: Maintain a chronology of who you spoke with, dates, names, and reference numbers. This record speeds up any appeal or TAS referral.
Common mistakes taxpayers make
- Calling the wrong number or sending documents to the wrong address.
- Assuming the same process applies to all audits—LB&I and SB/SE audits differ materially.
- Waiting to seek TAS help when financial hardship is present—TAS can sometimes stop a levy or delay enforcement while resolving the underlying problem.
- Treating civil collection notices as criminal threats—only CI handles criminal investigations.
Frequently asked questions
Q: Who should I call if I get a notice about my individual tax return?
A: Most individual notices are handled by Wage & Investment (W&I). The notice will list the phone number for the appropriate IRS unit.
Q: My small business owes payroll taxes. Which division handles that?
A: Payroll and employment tax issues for small businesses are usually handled by Small Business/Self-Employed (SB/SE).
Q: I’m a nonprofit applying for 501(c)(3) status. Who reviews my application?
A: The Tax Exempt & Government Entities (TE/GE) division processes exemption applications and compliance reviews.
Practical examples from practice
- Example 1: A sole proprietor with overdue payroll deposits was assigned to SB/SE. Early contact with SB/SE and a timely installment plan avoided a trust fund recovery penalty referral.
- Example 2: A large multinational client with transfer-pricing scrutiny was handled by LB&I; coordinated document production and pre-audit meetings reduced the scope and duration of the audit.
Author’s note and disclaimer
I am a Certified Public Accountant (CPA) with over 15 years of experience advising individuals, small businesses, and large corporations on tax compliance, audits, and IRS interactions. The insights above reflect typical IRS practice and my professional experience. This article is educational and does not constitute legal or tax advice for your specific situation. For individualized guidance, consult a qualified CPA, Enrolled Agent, or tax attorney.
Sources and further reading
- IRS — About the IRS: https://www.irs.gov/about-irs (official overview of agency roles and organizational units).
- FinHelp glossary: Taxpayer Advocate Service (TAS): https://finhelp.io/glossary/taxpayer-advocate-service-tas/
- FinHelp glossary: How to File an Administrative Appeal with the IRS Office of Appeals: https://finhelp.io/glossary/how-to-file-an-administrative-appeal-with-the-irs-office-of-appeals/
Last updated: August 19, 2025
Professional disclaimer: This content is for educational purposes only and should not be taken as individualized tax or legal advice.