Short answer
A cost segregation practice can operate as a sole proprietorship, a limited liability company, a partnership or a corporation. The choice affects how the business is taxed, what it files, how owners are paid, how liability between the business and its owners is separated under state law, and how the practice looks to clients and lenders. It does not change the practitioner's personal responsibility for the quality of a study, the professional rules that apply to licensed advisers, or the need for insurance, contracts and a reviewer. This article describes what each structure changes and does not change, and lists the questions to bring to an attorney and a tax adviser in your state. It is general education, not legal or tax advice, and NBCSS does not recommend any structure or provider.
What the structures are
The IRS describes the common structures and notes that the choice affects taxation and filing. In outline:
| Structure | Created by | Default federal tax treatment | Typical use |
|---|---|---|---|
| Sole proprietorship | Doing business as yourself; no filing beyond any local registration | Income on the owner's return; self-employment tax on net earnings | A single practitioner starting out |
| Limited liability company (LLC) | State filing | One member: disregarded, taxed like a sole proprietorship; two or more: partnership; may elect corporate treatment | Single practitioners and small groups wanting a state-law entity |
| Partnership | Agreement between two or more owners; state filing for limited forms | Partnership return; income passes to partners; self-employment tax for general partners | Two or more practitioners sharing a practice |
| Corporation | State filing | Corporate tax, or S corporation election to pass income through | Larger practices; owners paid as employees |
State law governs formation, ongoing filings, fees and the separation of liability. Federal tax classification follows the IRS rules, including the LLC default and election rules. An employer identification number is obtained from the IRS online at no charge; no paid service is needed for that step.
What the structure changes
- Taxation and filing. Whether income is reported on your return, a partnership return or a corporate return; whether self-employment tax or payroll taxes apply to owner compensation; which forms are due when.
- Liability separation under state law. An entity can separate the business's contractual and some other obligations from the owner's personal assets, subject to conditions state law sets and to exceptions for an individual's own professional conduct.
- Ownership and succession. How partners or shareholders join and leave, how profits are shared, what happens on death or disability.
- Administration. Registrations, annual reports, separate accounts and records, and the discipline of keeping business and personal affairs apart, without which the entity's protections weaken.
- Perception. Clients, lenders and firms that refer work sometimes prefer to contract with an entity.
What the structure does not change
- Your responsibility for the study. The IRS guide expects a quality study to identify the preparer and their credentials; an examiner asks the person, not the entity. Practitioners who practice before the IRS remain personally subject to Circular 230's competence and diligence standards through any entity.
- Professional liability for your own work. Entity separation under state law generally does not shield an individual from liability for their own professional acts. Insurance and engagement terms address that; the entity does not.
- Licensing obligations. Engineers, CPAs and appraisers carry their license rules into the practice, and some states restrict which entity forms licensed professionals may use.
- The need for a reviewer, contracts and records. None of these is supplied by a filing.
Questions to take to counsel and a tax adviser
- Which structures does my state allow for the services I provide, given any professional license I hold?
- What does each structure cost to form and maintain here, in fees and filings?
- How will owner compensation be taxed under each, given expected income?
- What does entity separation actually protect against in my state, and what does it not?
- How should partners share profits, decide disputes and exit?
- What records and formalities must I keep for the separation to hold?
- What changes if I add employees, a second office or an out-of-state client?
- Do any of my referral sources or clients require a particular form?
Take the answers as a set. Choosing a structure for one reason, such as a perceived tax saving, and ignoring the others is how practices end up reorganizing in year two.
How clients and advisers see the structure
The tax adviser who relies on your study contracts with whoever signs the engagement letter, and wants to know who stands behind the work. An entity name on the letter with no individual identified is a weaker answer than an entity name with a named preparer and reviewer, which is also what the IRS guide expects to see in the report itself. Firms that refer work often ask for a certificate of insurance naming the entity, a W-9 with the entity's classification, and evidence that the entity is in good standing with the state. Keeping those three current is part of running the structure, not a one-time task at formation.
Owner compensation and the practice's cash
Each structure pays its owners differently. A sole proprietor or single-member LLC owner takes draws and pays self-employment tax on net earnings. Partners take distributions and, where the agreement provides, guaranteed payments, a term of art for fixed payments for services that does not describe any promise about results. An S corporation pays its owner-employees wages through payroll and distributes the rest, which changes payroll obligations and record-keeping and is one of the reasons the S election is often discussed. None of these choices changes what the practice earns; they change how it is taxed and administered, and the adviser's model should show the whole picture, including state taxes and the cost of the additional filings, before the choice is made on the strength of one line.
Changing structure later
Practices reorganize: a sole proprietor forms an LLC when the first employee is hired, a partnership incorporates when a third partner joins, an LLC elects S treatment when income grows. Each change has tax and administrative consequences and a right order of steps, and some are hard to reverse. Engagement letters, insurance, bank accounts, registrations and referral agreements all have to move with the entity. Plan the change with counsel and the adviser before the year in which it takes effect, and tell clients and referral sources what changed and when.
About paid formation services
Formation services and business-resource vendors advertise to new practitioners, and some professional bodies have commercial relationships with them. NBCSS's position is that education comes first and any commercial relationship is disclosed beside the recommendation. For the record: an EIN is free from the IRS; state filings can be made directly with the state; and the questions above are for a licensed attorney and a tax adviser, not for a formation website. If NBCSS ever lists a formation partner, the listing will say what the relationship is.
A sequence that works
- Decide what the practice will do and with whom, in writing.
- Get the state and licensing constraints from counsel.
- Model the tax result with an adviser under two or three structures.
- Choose, form, obtain the EIN, open separate accounts.
- Put engagement letters, insurance and the reviewer arrangement in place before the first client.
- Calendar the filings.
What people ask on Reddit and other forums
The searches that lead people to these threads are usually phrased "LLC for cost segregation business", "start a cost segregation firm", "S corporation cost segregation practice".
"Should I form an LLC first" is the standard opening question in the r/smallbusiness and "cost segregation reddit" threads about starting a practice. From the sources below:
"Do I need an LLC to do cost seg?" No structure is required to practice. An entity is a choice about taxation, administration and state-law liability separation, made with counsel.
"Will an LLC protect me if a study is wrong?" Entity separation generally does not shield you from liability for your own professional work. That is what professional liability insurance and clear engagement terms are for.
"S corp for the tax savings?" It depends on income, compensation and state rules. Model it with an adviser rather than adopting a rule of thumb.
"Do I have to pay a service for an EIN?" No. The IRS issues EINs online at no charge.
Questions people also ask
Do I need an LLC to do cost segregation work?
No. No structure is required to practice. An entity is a choice about taxation, administration and state-law liability separation, made with counsel.
Does an LLC protect me if a study is wrong?
Entity separation under state law generally does not shield you from liability for your own professional work. Professional liability insurance and clear engagement terms address that risk.
Is an S corporation better for taxes?
It depends on income, compensation and state rules. Model it with a tax adviser rather than adopting a rule of thumb.
Do I have to pay for an EIN?
No. The IRS issues EINs online at no charge.
Can a CPA or engineer form any kind of entity for this work?
State licensing rules may restrict entity forms for licensed professionals. Ask counsel in your state.
Sources
- https://www.irs.gov/businesses/small-businesses-self-employed/business-structures — IRS, Business Structures.
- https://www.irs.gov/businesses/small-businesses-self-employed/limited-liability-company-llc — IRS, Limited Liability Company (LLC).
- https://www.irs.gov/businesses/small-businesses-self-employed/get-an-employer-identification-number — IRS, Get an employer identification number.
- https://www.irs.gov/businesses/small-businesses-self-employed/self-employment-tax-social-security-and-medicare-taxes — IRS, Self-Employment Tax.
- https://www.irs.gov/pub/irs-pdf/pcir230.pdf — Treasury Department Circular No. 230: §10.22, §10.35.