The Cliff Ahead: Understanding the Section 199A Sunset
For nearly a decade, the Qualified Business Income (QBI) deduction under Internal Revenue Code Section 199A has served as the cornerstone of tax planning for owners of pass-through entities. Enacted as part of the Tax Cuts and Jobs Act (TCJA) of 2017, Section 199A allowed eligible owners of sole proprietorships, partnerships, and S corporations to deduct up to 20% of their qualified business income, effectively lowering the top marginal rate on pass-through earnings from 37% to an effective rate closer to 29.6%.
Absent congressional intervention, Section 199A is scheduled to sunset at the end of 2025. Beginning January 1, 2026, that 20% deduction disappears. For business owners who have structured their operations, compensation, and even entity elections around this benefit, the sunset is not a minor adjustment. It is a structural shift that demands a fresh look at entity choice, compensation planning, and long-term tax architecture.
This article examines the strategic pivot that sophisticated business owners and their advisors should be evaluating now, with particular attention to the mathematics governing the perennial question: does it make sense to convert a pass-through entity to a C corporation?
Why the Sunset Changes the Calculus
Under current law, the corporate tax rate enacted by the TCJA remains fixed at a flat 21%, and that rate is not scheduled to sunset. This asymmetry is the crux of the post-2025 planning problem.
Consider the comparison:
- Pass-through entities after 2025: Business income is taxed at the owner's individual marginal rate, up to 37% federal, without the benefit of the 20% QBI deduction that previously softened that top rate.
- C corporations: Business income is taxed at a flat 21% federal corporate rate, with a second layer of tax imposed only when earnings are distributed as dividends (generally taxed at qualified dividend rates, currently up to 20%, plus the 3.8% Net Investment Income Tax where applicable).
At first glance, the C corporation route appears markedly more favorable once the QBI deduction disappears. But the analysis is more nuanced than comparing 21% to 37%. The double-taxation structure of C corporations means that the ultimate rate owners face depends heavily on whether and when earnings are distributed.
The Mathematical Threshold: Retained Earnings vs. Distributions
The strategic value of C-corporation conversion turns largely on a single variable: the owner's intent regarding distributions.
If earnings are retained and reinvested in the business:
A C corporation paying a flat 21% rate on retained earnings, with no immediate second layer of tax, can outperform a pass-through entity taxed at 37% on the same income with no QBI offset. For businesses with significant capital expenditure needs, expansion plans, or a long runway before liquidity events, retained C-corp earnings can compound more efficiently.
If earnings are distributed annually to owners:
Once dividends are paid, the effective combined rate on C-corporation income can approach or exceed the top individual pass-through rate. A rough calculation illustrates the point:
- Corporate level tax: 21%
- Remaining earnings: 79 cents on the dollar
- Dividend tax at 20% (plus 3.8% NIIT, where applicable): reduces the 79 cents by roughly 18.8%
- Effective combined rate: approximately 35.8%–36%
This is strikingly close to the 37% top individual rate that pass-through owners will face without QBI. The conversion decision, therefore, is not a clear win for C-corp status in every case. It is highly sensitive to:
- The owner's distribution habits and cash-flow needs
- State-level tax treatment (many states do not conform to federal pass-through rules identically)
- The anticipated holding period and potential for a future sale
- Eligibility for Section 1202 Qualified Small Business Stock (QSBS) exclusion, which can make C-corp status significantly more attractive for exit-oriented businesses
QSBS: The Wildcard That Changes the Analysis
For businesses anticipating a sale or exit within a five-to-ten-year horizon, Section 1202 deserves particular attention. Qualified Small Business Stock, if held for more than five years and issued by a qualifying C corporation, can allow shareholders to exclude a substantial portion of gain on sale, subject to per-issuer and per-taxpayer limitations that vary based on when the stock was acquired.
For founders and investors in eligible industries, this benefit alone can tip the scale toward C-corp conversion, independent of the annual rate comparison. However, QSBS eligibility carries strict requirements regarding the nature of the business, gross asset limitations at issuance, and active business requirements that must be carefully vetted before conversion.
Practical Considerations Before Converting
Entity conversion is not merely a tax election. Business owners contemplating a shift from pass-through to C-corporation status should evaluate:
- Built-in gains and asset step-up issues, particularly for entities converting from S corporation status with appreciated assets
- State tax conformity, since state treatment of QBI and corporate rates varies widely and can materially affect the net analysis
- Exit strategy timing, since converting shortly before a planned sale can forfeit favorable capital gains treatment available to pass-through sellers
- Compensation structuring, since C-corp owners who also serve as employees must navigate reasonable compensation rules to avoid unnecessary payroll tax exposure
The Strategic Takeaway
The scheduled expiration of Section 199A transforms a once-static planning assumption into an active decision point. Owners who have treated pass-through status as a permanent fixture of their tax planning should revisit that assumption now, not in December 2025.
The mathematics favor no single universal answer. Businesses with strong reinvestment needs, long time horizons, and QSBS eligibility may find C-corporation conversion compelling. Businesses with high distribution needs, shorter horizons, or state tax environments unfavorable to corporations may find that remaining a pass-through entity, even without QBI, remains the more efficient structure.
What is clear is that the decision requires modeling specific to each business's cash flow patterns, growth trajectory, and ownership objectives. Waiting until the sunset takes effect to run these numbers leaves little room for the multi-year planning that optimal restructuring often requires.