Trading Entity Selection: Sole Proprietor, LLC, S-Corp

The legal entity a trader chooses affects liability, taxation, retirement options, and administrative cost. The choice is not permanent, but changing it mid-stream is expensive. The framework below sorts the three common structures by the criteria that actually matter for a trading business.

Sole proprietor (default)

A sole proprietorship is the default — no filing required. You and the business are the same legal entity.

• Liability: unlimited personal liability. A trading debt or lawsuit reaches personal assets.
• Taxation: Schedule C profit flows to personal return; self-employment tax applies only if the activity is a "business" not "investing" — traders usually escape SE tax, but the distinction is fact-specific.
• Retirement: Solo 401(k) and SEP-IRA available.
• Cost: $0 to maintain, beyond normal tax filing.

Best for: traders just starting, under $50k capital, testing whether the activity is viable.

Single-member LLC

An LLC is a state-level entity that provides a liability shield between the business and the owner. A single-member LLC is taxed as a disregarded entity by default (same as sole proprietor) but can elect S-Corp or C-Corp treatment.

• Liability: members generally not personally liable for LLC debts. The shield is not absolute — fraud and personal guarantees pierce it.
• Taxation: default disregarded (Schedule C); elective S-Corp or C-Corp.
• Retirement: same retirement options as sole proprietor if disregarded.
• Cost: $50–$500 formation, $0–$800 annual state franchise fee (California is the expensive outlier), separate accounting and bank account required.

Best for: traders with meaningful capital seeking liability separation without corporate complexity.

S-Corp election

An LLC or C-Corp can elect S-Corp status (Form 2553). S-Corps pass income through to owners but allow a salary/dividend split that can reduce self-employment tax.

• Liability: same shield as LLC.
• Taxation: pass-through, but owner must take a "reasonable salary" subject to payroll tax; remaining profit distributes without SE tax. For traders, this is the key benefit only if SE tax would otherwise apply.
• Retirement: Solo 401(k) on salary; higher contribution limits via salary.
• Cost: payroll processing ($500–$1,500/year), separate tax return (Form 1120-S, $500–$1,500 prep), stricter bookkeeping.

Best for: profitable traders whose CPA confirms SE tax exposure, typically netting $80k+ from trading as a business.

The decision matrix

1. Capital under $50k, < 1 year track record: sole proprietor. Keep overhead zero.
2. Capital $50k–$250k, established track record: single-member LLC for liability, taxed as disregarded.
3. Net trading income $80k+, confirmed trader-tax status: LLC electing S-Corp, with a CPA managing payroll and the 1120-S.
4. Trading others' capital or managing accounts: LLC or LLC electing S-Corp is mandatory for liability — never manage outside capital as a sole proprietor.

Critical caveats

• Trader tax status (Section 475) is separate from entity choice; an LLC does not grant it.
• State fees vary wildly; California charges $800 minimum franchise tax regardless of profit.
• Commingling personal and entity funds destroys the liability shield — maintain separate accounts and document transactions.