C-Corp vs Pass-Through Decision Framework
"TCJA dropped the corporate rate from 35% to 21%. Half the founders in Silicon Valley restructured. Half should have. Knowing which half you're in is a five-million-dollar question."
The 60-second pitch
For 30 years, conventional wisdom said: "always pass-through." C-corps had 35% federal tax + double taxation on dividends. Total burn rate on distributed profit: ~55%. Pass-throughs (S-corp, partnership, LLC) paid one layer of tax at the owner's individual rate.
TCJA broke the rule. In 2018, the C-corp rate dropped to 21%, flat, forever. Pass-through top rate stayed at 37% federal, partially offset by the 20% QBI deduction (which phases out for service businesses above ~$242K AGI in 2024). For the first time in a generation, C-corp could be the cheaper structure — but only if you understood the second layer.
The second layer is dividends. When a C-corp pays $1 of after-tax profit to the owner, the owner owes capital-gains rate on it (15% or 20% federal + 3.8% NIIT). $100 of pre-tax profit → $79 after C-corp tax → $63 after 20% LTCG dividend tax. That 37% all-in is essentially identical to the pass-through top rate.
So the math turns on what you do with the after-tax profit at the corporate level. Retain it and reinvest it in R&D, equipment, or working capital? C-corp wins big — you get 79¢ on the dollar working for you vs. 60¢ in a pass-through. Pay it out as salary or dividend every year? Pass-through ties or wins. Plan a QSBS §1202 exit? C-corp wins by millions — up to $15M of gain (or 10× basis) is permanently tax-free for stock issued after July 4, 2025 ($10M for older stock).
The decision isn't ideology. It's modeling. Run the numbers for your facts.
Real-world example
The setup. Marco bootstrapped a SaaS for utility companies. 2025 net profit: $500,000. He'd like to pay himself ~$200K to live on and reinvest the rest into engineering hires. He's targeting a $50M acquisition exit in ~5 years. Federal marginal at top dollar: 37%. State (MA): 5%.
Path A: S-corp. Marco takes $150K W-2 (reasonable comp for solo founder), passes through $350K K-1 at 37% federal + 5% state = $147,000 federal/state tax. He'd reinvest the rest, but post-tax. Total annual federal: ~$148K. After-tax retained for reinvestment: $203K.
Path B: C-corp. Marco takes $200K W-2 (deductible to corp). Corp earns $300K pre-tax, owes 21% = $63K. Corp retains $237K after-tax. Marco pays personal tax only on the $200K W-2 (37% federal = $74K). Total annual federal: $137K. After-tax retained for reinvestment: $237K — $34K more reinvestment capital every year.
The QSBS kicker. Marco's C-corp is a Qualified Small Business (under $50M in assets at issuance, not an excluded business). He held founder shares for > 5 years. Sale price 2030: $50M. His basis: $0. Without QSBS: $50M × 23.8% = $11.9M federal tax. With QSBS §1202 (greater of $10M or 10× basis exclusion): $10M tax-free, $40M taxable at 23.8% = $9.52M tax. Savings: $2.38M.
And there's more. Under post-OBBBA (2025) QSBS expansion, the cap goes to $15M (or 10× basis) for stock issued after July 4, 2025, with tiered exclusion at 3/4/5 years. If Marco issues new C-corp stock post-OBBBA and holds 5+ years: $15M permanently tax-free.
The decision framework
- Map your business to one of five archetypes.
(a) Service business, owners take everything → pass-through
(b) Capital-intensive, retains earnings → C-corp candidate
(c) R&D-heavy or VC-track startup → C-corp (QSBS)
(d) Holding company for investments → C-corp (or PHC trap; see below)
(e) Real estate operating company → pass-through (REPS, depreciation) - Compute your "distribution ratio." What % of annual profit do you actually pay out vs. retain? Above 80% paid out → pass-through. Below 40% paid out → C-corp candidate.
- Check QBI eligibility. Under the SSTB rules (§199A), high-income owners (> $241,950 single / $483,900 MFJ for 2024) in law, health, accounting, consulting, financial services, athletics, performing arts, or "principal asset is reputation" — phase out of QBI. If you're an SSTB phased out, pass-through has a hidden cost.
- Model QSBS qualification. §1202 requires: C-corp (not S-corp); aggregate gross assets at and immediately after stock issuance under $50M (stock issued on/before July 4, 2025) or under $75M (issued after); "qualified trade or business" (not SSTB, not banking, not farming, not extractive, not hotel/restaurant); 5-year hold. If you'll qualify and you're targeting an exit, C-corp is a no-brainer.
- Watch for the §531 accumulated earnings tax. A C-corp accumulating earnings beyond "reasonable business needs" past $250K (or $150K for personal service corps) can face a 20% accumulated earnings tax. Defense: Document growth plans; reinvest actively in R&D, hires, equipment.
- Watch for the §541 personal holding company (PHC) tax. A C-corp where 60%+ of income is passive (dividends, interest, royalties, rents) and 50%+ ownership is by ≤ 5 individuals — additional 20% tax on undistributed PHC income. Defense: Don't park investment portfolios in C-corp.
- Account for state tax overlay. Some states (CA, TX, IL) have flat franchise/income taxes on C-corps that crush the federal benefit. Others (NV, WY, DE, SD) are corp-friendly. Model state tax.
- Time the transition. S-corp → C-corp: revoke S-election (Form 1120-S with revocation statement); auto C-corp next year. C-corp → S-corp: file Form 2553 by 3/15. Watch for BIG (built-in gains) tax on a C→S conversion of appreciated assets within 5 years.
- For new businesses: incorporate as C-corp and file Form 2553 the same week. This gives you C-corp legal structure with S-corp taxation — and reversibility. You can revoke S-election later without re-incorporating.
- If keeping C-corp: implement an accountable plan, set reasonable comp on W-2, and time bonuses around 12/31. C-corps have a calendar-year fiscal-year flexibility advantage (most are 12/31, but you can choose).
- Document with a memo. The entity choice memo should include: 5-year distribution forecast, QBI eligibility status, QSBS plan, state tax overlay, exit strategy. Sign it. File it in the corporate book.
- Revisit every 3 years. Tax law, your distribution ratio, and your exit timeline all change. A C-corp that made sense in 2018 may need to be S-corp by 2026.
IRS code & authority
- IRC §11 C-corp tax — flat 21% post-TCJA.
- IRC §1361 – §1379 Subchapter S rules — eligibility, election, termination of S-corp status.
- IRC §199A The QBI deduction — 20% of qualified business income, phased out for SSTBs above the threshold.
- IRC §1202 Qualified Small Business Stock — up to $10M (or 10× basis) of gain exclusion on C-corp stock held > 5 years. 2025 OBBBA expansion: $15M cap, tiered 3/4/5-yr exclusion for stock issued after July 4, 2025.
- IRC §1045 QSBS rollover — defer gain by reinvesting in another QSBS within 60 days.
- IRC §531-537 Accumulated Earnings Tax — 20% penalty tax on C-corp earnings retained beyond reasonable business needs.
- IRC §541-547 Personal Holding Company tax — 20% penalty tax on undistributed PHC income.
- IRC §1374 Built-in gains tax on S-corp converted from C-corp; applies to appreciated assets sold within 5 years.
- IRC §269A / §482 Anti-shifting rules for related-party C-corp / pass-through arrangements.
- Form 2553 S-corp election.
- Form 8832 Entity classification election (LLC → C-corp or partnership).
- Rev. Proc. 2013-30 Late S-corp election relief (separate strategy).
Decision risk flags
- Double tax on dividends. The single biggest C-corp risk. Every $100 distributed becomes ~$60 in the owner's hand. Defense: Don't distribute unless you have to. Reinvest. Pay reasonable comp.
- Accumulated earnings tax (§531). Sitting on cash without a business reason = 20% penalty tax. Defense: Documented growth/R&D/acquisition plans; reasonable retention.
- Personal holding company tax (§541). If your C-corp's income is mostly passive (rents, royalties, dividends) and ≤5 owners — 20% additional tax. Defense: Keep operational business activity central; don't park investments.
- Losing QSBS by conversion. Converting an S-corp to C-corp does NOT make existing stock QSBS-eligible. The 5-year clock starts at original issuance after C-corp election. Defense: If QSBS matters, start as C-corp.
- Built-in gains tax on C→S conversion. Selling appreciated assets within 5 years of conversion = double tax. Defense: Don't convert near a sale; wait or restructure.
- S-corp single-class-of-stock rule. Disproportionate distributions, preferred stock, second class of stock = termination of S-election. Defense: Keep capital structure simple; no founder preferred shares.
- S-corp 100-shareholder limit. Hard cap. C-corp = unlimited. Defense: Pass-through unsuitable if you're raising real venture money.
- Foreign owners. S-corp can't have non-resident alien shareholders. C-corp can. Defense: If you'll take foreign investment, C-corp.
- State franchise tax surprises. CA $800 minimum + 8.84% corporate tax. TX franchise tax. NY MTA surcharge. Defense: Model state load before choosing.
When NOT to choose each path
- Don't go C-corp if: you pay out 70%+ of profit annually as cash to live on (double-tax kills the benefit).
- Don't go C-corp if: you're a service business with no QSBS path (you'll never get the §1202 exit win to justify the dividend tax).
- Don't go C-corp if: your business is real estate operating (depreciation losses get trapped at the corporate level; flow-through is dramatically better).
- Don't go S-corp if: you're a VC-track startup raising preferred stock — single-class-of-stock rule and shareholder caps make it impossible.
- Don't go S-corp if: you have foreign or institutional investors — eligibility rules block them.
- Don't go S-corp if: your business is a "personal service corporation" with very few owners and high passive income — PHC rules can apply.
- Don't go partnership/LLC if: you'll have stock-comp-like equity structures with vesting (S-corp single-class issues, partnership profits-interest complexity).
Run the entity decision on your numbers
PilePilot's Books agent models C-corp vs S-corp vs partnership using your real distribution ratio, state tax overlay, and QSBS eligibility — and produces the memo you'd want in your corporate book. Built for small businesses who has restructured dozens of clients in both directions.
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Disclaimer. This page is educational and not tax advice. Entity choice is a permanent, high-stakes decision with federal, state, and exit-strategy interactions. Before changing entity structure, work with a qualified tax professional and corporate attorney. All dollar examples are illustrative; your actual outcome depends on profit, distribution policy, marginal rates, state law, and exit plans.