Firm legal structures: sole proprietorship, partnership, LLP, LLC, PC, and corporations compared

One-line orientation

A firm’s legal structure affects taxes and liability for business debts or other people’s acts. It does not protect a licensed professional from liability for their own negligence.

Key points

• Sole Proprietorship: One owner; the business may operate under the owner’s name or a trade name. Easy to set up and fully owner-managed, but the owner is personally liable for all debts, losses, and claims. No separate business entity exists.
• General Partnership: Two or more architects share management, profits, and risk. No formal entity is created; each partner is personally liable for the other partners’ actions. A written partnership agreement is essential but does not remove personal liability.
• Limited Partnership: At least one general partner (manages, is fully liable) and at least one limited partner (receives profit share, not involved in management, liable only up to their investment).
• Limited Liability Partnership (LLP): A distinct legal entity. An LLP can limit a partner’s liability for many firm debts and another partner’s acts, but not for that partner’s own negligence. This is a common protective structure for professional service firms, especially where licensing rules constrain LLC use.
• Corporation (C-corp): A separate legal entity with stockholders, directors, and officers. Shareholders’ personal assets are protected. A C-corporation may issue stock, but most architecture corporations are closely held rather than publicly traded or outside-owned. Subject to double taxation (corporate-level tax on profits + personal tax on dividends).
• S-Corporation: Similar to a C-corp but with eligibility limits (shareholder count/type and one class of stock). Shareholders are often firm employees involved in management. Pass-through taxation — income and losses flow directly to shareholders’ personal returns; no corporate-level tax on profits.
• Professional Corporation (PC): A corporate form for licensed professional services. State law controls whether a PC is required, who may own/manage it, and whether licensed architects must hold a certain percentage of ownership or control.
• Limited Liability Company (LLC): Hybrid structure combining liability protection of a corporation with the simplified pass-through tax treatment of a sole proprietorship or partnership. Less formal than a corporation, but not every jurisdiction permits architecture firms to practice through an LLC.
• Joint Venture: A temporary association of two or more firms to complete a specific project. Based on a formal written agreement; not a permanent firm structure.
• Written agreements are non-negotiable when forming a firm: cover monetary contributions, profit/loss allocations, ownership transfer, confidentiality, and restrictive covenants or client-protection terms where enforceable.
• Out-of-jurisdiction practice: working in a new state or territory requires compliance with that jurisdiction’s individual license, firm registration, and business-entity requirements. Often this means foreign qualification / certificate of authority plus firm registration; in some states, entity-type restrictions may require forming or converting into a different entity.

Firm legal structures: the personal-liability spectrum

Liability runs from exposed (full personal liability) to protected; a limited partnership is split. All are pass-through taxed except the C-corp.

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Key

• full personal liability
• split (GP / LP)
• protected

A written partnership agreement does not create liability protection — only forming an LLP / LLC / corporation does. Only the C-corp is double-taxed.

LLP = limited liability partnership · LLC = limited liability company · S-corp and C-corp = the two corporation tax elections. A joint venture is not another structure on this scale — it is a temporary association formed for one project, and each venturer brings its own entity and its own liability.

Confusions / comparison

Entity	Personal liability	Taxation	Ownership / management notes
Sole proprietorship	Full — unlimited	Personal return only	Single owner; easiest to form
General partnership	Full — each partner liable for others	Pass-through (individual returns)	Written agreement critical
Limited partnership	GP = full; LP = limited to investment	Pass-through	LP has no management role
LLP	Often protected from firm debts and others’ acts; not one’s own negligence	Pass-through (individual returns)	State law controls the exact protection
LLC	Protected	Pass-through (default)	Hybrid; flexible management
S-Corporation	Protected (shareholders)	Pass-through	Eligibility limits; shareholders often employees
C-Corporation	Protected (shareholders), except personal professional responsibility	Double taxation	Separate entity; closely held firms are common
Professional Corporation (PC)	Protected, except personal professional responsibility	Depends on tax election	State licensing law controls ownership/management
Joint venture	Agreement governs internal risk allocation; outside claims may differ	Depends on the participating entities and agreement	Temporary association of two or more firms for one specific project; not a permanent firm structure

Key concept traps

Common confusion	Correct answer
”A written partnership agreement eliminates personal liability in a general partnership”	No — it governs the relationship but does not create liability protection; only forming an LLP or LLC does
”My firm’s license covers all U.S. jurisdictions”	No — each jurisdiction requires separate individual licensure, firm registration, and entity compliance; out-of-state work may require foreign qualification or a different entity
”S-corp and C-corp are taxed the same way”	No — S-corp = pass-through; C-corp = double taxation

Related

→ NCARB model rules and licensure (this module): what it means to be licensed in a jurisdiction → pp-ncarb-rules-vs-aia-ethics: firm conduct obligations once the firm is formed → pp-stamp-seal-responsible-control: the licensed architect’s personal responsibility within whatever firm structure is used