What Is Considered Professional Services: Federal Fields and Tax Rules

Professional services, in the sense the law uses the term, are work whose value comes from a practitioner’s specialized expertise and judgment rather than from a physical product. Federal tax law identifies eight core fields as professional services: health, law, engineering, architecture, accounting, actuarial science, performing arts, and consulting.¹ That classification is not just descriptive. It changes how a business can be taxed, who is allowed to own it, what licensing it needs, and how it’s judged when something goes wrong.

What Makes a Service “Professional”

The defining trait is that the client is paying for judgment and knowledge, not for an object. A surgeon isn’t selling the hip replacement; the patient is paying for the surgeon’s ability to install it correctly. A tax attorney isn’t selling a contract; the client is paying for an analysis of how to structure a deal. The output is advice, diagnosis, design, or skilled decision-making applied to a specific problem.

Most of these roles require advanced education — typically a graduate degree or professional doctorate — along with a licensing or certification exam. But the credential itself isn’t the real marker. The marker is the expectation that the practitioner will exercise independent judgment the client cannot replicate. That asymmetry is what the legal system treats differently from an ordinary purchase, and it’s what the rest of the rules on this page build on.

The Eight Fields Federal Law Lists

Internal Revenue Code Section 448(d)(2) names the eight fields that qualify a corporation as a “qualified personal service corporation,” and that list is the closest thing federal law gives to a working definition of professional services.¹

Health. Physicians, surgeons, dentists, psychologists, and other licensed healthcare providers who diagnose or treat patients.
Law. Attorneys and other licensed legal practitioners who advise on or litigate legal matters.
Accounting. Certified Public Accountants and auditors who examine financial records, prepare tax filings, and verify compliance.
Engineering. Licensed engineers who apply scientific and mathematical principles to design systems, structures, or processes.
Architecture. Licensed architects who create building designs and structural plans that must satisfy safety and building codes.
Actuarial science. Actuaries who use statistical models to assess risk for insurance companies, pension funds, and financial institutions.
Performing arts. Actors, musicians, directors, and similar artists whose compensation is tied to their creative performance.
Consulting. Advisors who provide expert counsel in a specialized field, defined more narrowly than ordinary usage would suggest.

The list isn’t exhaustive for every purpose, but it governs the federal tax questions discussed below and tracks closely with what state licensing law treats as a regulated profession.

Why Consulting Is Narrower Than People Think

Consulting is the category that trips up the most business owners. Under IRS regulations, consulting means providing advice and counsel, and nothing more. If your pay depends on whether a transaction closes, or if you’re executing deals rather than just recommending them, the work is sales or brokerage, not consulting.²

The regulations give concrete examples. An economist who analyzes market conditions and advises a company on strategy is consulting. A financial planner who designs budgets and recommends investments is consulting. A securities broker who recommends investments and then executes the trades is not, because the pay rides on the transaction. A staffing firm that recommends candidates and earns a fee contingent on placement is doing brokerage, not consulting.²

The test is how you get paid. Flat or hourly fees that don’t move with the client’s decision are consulting. Compensation that rises or falls with a transaction the advice was supposed to produce usually isn’t. The distinction matters for both federal tax questions covered next.

Why the Classification Matters

Cash-Method Accounting for Qualified Personal Service Corporations

A business organized around any of the eight fields can elect to be treated as a qualified personal service corporation and use the cash method of accounting regardless of its gross receipts.¹ Other C corporations have to switch to accrual once their average annual gross receipts over the prior three years exceed $32 million for tax year 2026.³ Cash accounting recognizes income when received and deducts expenses when paid, which gives professional firms more control over the timing of tax.

Two tests apply. Substantially all of the corporation’s activities must involve services in one of the eight fields, and substantially all of its stock by value must be held by people who perform those services, retired employees who formerly did the work, or their estates and heirs (heirs only for two years after death).¹ IRS regulations set “substantially all” at 95 percent or more.² A law firm with 10 percent of its equity in a private equity fund fails the ownership test and loses the election.

The Section 199A Deduction and Specified Service Trades

Section 199A gives owners of pass-through businesses — sole proprietors, S corporation shareholders, and partners — a deduction of up to 20 percent of their qualified business income.⁴ For most professional service fields, that deduction phases out above an income threshold and disappears above a higher one.

The law labels certain fields “specified service trades or businesses” (SSTBs): health, law, accounting, actuarial science, performing arts, consulting, athletics, financial services, and brokerage services. Engineering and architecture are deliberately left off this list even though they appear in the Section 448 definition.⁴ An engineer or architect running a pass-through firm can claim the full QBI deduction at any income level. An attorney or physician at the same income faces a phase-out.

For tax year 2026, the SSTB phase-out starts at taxable income of $201,750 for single filers or $403,500 for joint filers, and the deduction is gone entirely at $276,750 single or $553,500 joint.³ Below those thresholds the SSTB label doesn’t affect the deduction. Above them it can be worth tens of thousands of dollars a year.

State Ownership Rules: PCs and PLLCs

Most states require licensed professionals to organize under a Professional Corporation (PC) or Professional Limited Liability Company (PLLC) rather than a standard entity. These structures mirror the federal ownership principle: only individuals holding the relevant license can be owners. A physician cannot form a standard LLC and bring in unlicensed business partners as co-owners; the state will require a PLLC in which every member holds a medical license. The specifics vary by state, but the rule is consistent — the people exercising professional judgment are the people who own the firm.

Licensing and Unauthorized Practice

What ultimately separates a professional service from ordinary expertise is that the government controls who can perform it. Practicing law, medicine, accounting, engineering, or architecture without the required license is a criminal offense in every state. Penalties range from misdemeanor charges carrying fines and up to a year in jail to felony charges with higher fines and possible prison time, depending on the field and the harm done.

Each profession is overseen by a state licensing board that sets education requirements, administers exams, and enforces ethics rules. These boards handle public complaints and can impose discipline up to full license revocation. Attorney discipline usually rests with the state court system, physicians answer to a medical board, CPAs to a state board of accountancy. Most states also require continuing education for renewal, and letting a license lapse — even by missing a renewal date — can create both unauthorized practice problems and gaps in malpractice coverage.

Standard of Care and Malpractice Exposure

When a professional’s work causes harm, courts don’t ask whether the practitioner acted like a reasonable person. They ask whether the practitioner acted like a competent professional in the same field under the same circumstances. That’s the malpractice standard of care, and it’s harder to satisfy than ordinary negligence. A surgeon is judged against other competent surgeons with similar training, not against a careful layperson.

Proving what that standard looks like almost always requires expert testimony. Federal Rule of Evidence 702 allows a witness to testify as an expert if qualified by knowledge, skill, experience, training, or education, and if the testimony rests on sufficient facts, reliable methods, and a sound application of those methods.⁵ A plaintiff suing an architect for a defective design generally needs another architect or structural engineer to testify about what the standard required and how the defendant fell short.

The plaintiff also has to prove causation — a direct link between the professional’s failure and the harm. A misdiagnosis isn’t malpractice if the correct diagnosis would have produced the same outcome. A missed deadline isn’t actionable if the underlying claim had no merit. Many malpractice cases fail here, because the client must prove not just the mistake but that the mistake changed the result.

Professional Liability Insurance

Because of that exposure, most professionals carry liability insurance, often called malpractice or errors-and-omissions coverage. Only a handful of states require it for attorneys, but a single malpractice verdict can exceed a practitioner’s net worth, so going without it is a serious risk.

Policies come in two basic forms, and the difference matters more than most buyers realize:

Occurrence policies. Cover any incident that happens while the policy is active, regardless of when the claim is filed. An occurrence policy in force in 2024 still covers a 2028 lawsuit over 2024 conduct, even if the practitioner has retired.
Claims-made policies. Cover a claim only if the practitioner is insured both when the incident happens and when the claim is filed. Canceling or switching insurers leaves incidents from the old period uncovered unless the practitioner buys separate protection.

That separate protection is called tail coverage, letting a retired or departing professional report later claims tied to incidents during the old policy. The alternative, bought from the new insurer, is nose coverage, which picks up the prior acts. Claims-made policies generally cost less year to year; occurrence policies cost more but never require a tail.

A Note on Sales Tax

Historically, most states exempt traditional professional services from sales tax — you don’t pay sales tax on an attorney’s bill or an accountant’s invoice the way you would on a retail purchase. That picture is shifting. States have been widening their sales tax bases, including into business-to-business services, and the specifics vary sharply from one state to the next. If you provide or buy professional services, the current rule in your state is worth checking directly, because this is one of the faster-moving areas of state tax law.

1
Office of the Law Revision Counsel. 26 USC 448 – Limitation on Use of Cash Method of Accounting
2
eCFR. 26 CFR 1.448-1T – Limitation on the Use of the Cash Receipts and Disbursements Method of Accounting (Temporary)
3
Internal Revenue Service. Revenue Procedure 2025-32
4
Office of the Law Revision Counsel. 26 USC 199A – Qualified Business Income
5
Legal Information Institute (LII) / Cornell Law School. Rule 702 – Testimony by Expert Witnesses