S-Corp R&D Tax: Immediate Deductions Under Section 174A

The S-Corp R&D tax deduction is back. The One Big Beautiful Bill Act (OBBBA) created new Section 174A, which restores immediate expensing of domestic research and experimental costs for tax years beginning after December 31, 2024 — permanently, not as a temporary patch. That reverses the most unpopular business provision of the Tax Cuts and Jobs Act, which forced companies to spread research deductions over five years starting in 2022.

But the headline change is only half the story. The transition rules are where 2026 planning actually happens, and they are on a clock. One election window — the small-business retroactive fix — already closed on July 6, 2026. Another, the catch-up deduction for costs you capitalized in 2022 through 2024, is claimed on the 2025 return, which for extended calendar-year S corporations is due September 15, 2026. If your S-Corp has been amortizing research costs, what you do before that filing deadline determines how fast you get those deductions back.

What Section 174A Changes for the S-Corp R&D Tax Deduction

From 2022 through 2024, old Section 174 required every business — including S corporations — to capitalize research and experimental expenditures and amortize domestic costs over five years (15 years for foreign research). A software firm that spent $500,000 on development in 2022 could deduct only a sliver of it that year, even though the cash was gone. For pass-through owners, phantom income flowed through to personal returns, and the S-Corp R&D tax deduction became a five-year installment plan.

For tax years beginning after December 31, 2024, Section 174A allows domestic research or experimental expenditures to be deducted in full in the year paid or incurred. A business that prefers to spread the deduction — for example, to preserve income against the QBI deduction or basis limitations — can instead elect to capitalize and amortize over a period of at least 60 months. The statute also says expressly that amounts paid or incurred in connection with software development are treated as research or experimental expenditures, which puts custom software, product development, engineering, and process-improvement work squarely in scope for many S corporations.

One important boundary remains: foreign research still gets no relief. Amended Section 174 now applies solely to foreign research or experimental expenditures, which must still be capitalized and amortized over 15 years. If your S-Corp uses overseas development contractors, those costs stay on the slow schedule — a deliberate congressional nudge toward onshore R&D.

The Catch-Up Deduction for 2022–2024 Costs: Still Open

What about the domestic research costs your S-Corp already capitalized under the old rules? OBBBA lets every taxpayer — regardless of size — recover the remaining unamortized 2022–2024 balance on an accelerated schedule. Rev. Proc. 2025-28 provides the procedures, and there are two options. The one-year option deducts the entire remaining unamortized amount in the first tax year beginning after December 31, 2024 — the 2025 return for calendar-year filers. The two-year option spreads that balance ratably over 2025 and 2026. For many owners, this catch-up is the single largest piece of the S-Corp R&D tax deduction in 2026.

Mechanically, this is an automatic accounting method change made with a statement in lieu of Form 3115, filed with the original return (including extensions) for that first post-2024 tax year. That is why the timing matters right now: a calendar-year S corporation on extension has until September 15, 2026 to file its 2025 Form 1120-S with the election statement attached. Choosing between one year and two is a planning decision, not a formality — a huge 2025 deduction is worthless to a shareholder who lacks the stock basis to absorb the loss, and it can crowd out other deductions that don’t carry forward as gracefully.

The Small-Business Retroactive Window Closed July 6, 2026

OBBBA also gave small businesses something better: the right to apply immediate expensing retroactively to 2022, 2023, and 2024 by amending those returns and claiming refunds. Eligibility ran through the Section 448(c) gross receipts test — average annual gross receipts for the three prior years of $25 million or less, inflation-adjusted to $31 million for tax years beginning in 2025 — excluding tax shelters.

Under Rev. Proc. 2025-28, that retroactive election had to be made by July 6, 2026 (or earlier, for 2022 years whose refund statute of limitations expired first). That deadline has passed. The same July 6, 2026 deadline applied to the companion late election under Section 280C(c)(2) to recompute the research credit on those amended returns. An S-Corp that missed the window has not lost the deductions themselves — the catch-up election above still recovers the full unamortized balance on the 2025 (or 2025–2026) returns. What’s gone is the ability to pull the refunds back into 2022–2024 and the interest that came with them.

The Deduction Is Not the R&D Credit — but They Interact

The S-Corp R&D tax deduction under Section 174A is separate from the research credit under Section 41. The credit has its own, narrower tests — the research must be technological in nature and involve a process of experimentation aimed at a new or improved business component. An S-Corp can qualify for both, and the credit, like the deduction, flows through to shareholders.

They interact through Section 280C(c): you must reduce your Section 174A deduction by the amount of the research credit, unless you elect the reduced credit — and that election is only available on an original, timely filed return. Claiming the credit also got more demanding. The redesigned Form 6765 adds Section G, which reports detailed business-component information. Section G is optional for tax years beginning before 2026 but generally required after that, with exceptions for qualified small businesses electing the payroll-tax credit and for filers with $1.5 million or less in qualified research expenses and $50 million or less in average gross receipts claiming the credit on an original return. If your documentation practices are thin, 2026 is the year to fix them.

What S-Corp Owners Should Do Before the 2025 Return Is Filed

Inventory the unamortized balance. Pull the 2022–2024 Section 174 schedules and confirm exactly what domestic balance remains — that number drives the one-year versus two-year decision. Check shareholder basis before supersizing the loss. A catch-up deduction that exceeds stock and debt basis is suspended at the shareholder level, so model the pass-through before electing the one-year option. Separate domestic from foreign spending. Only domestic costs qualify for expensing; foreign development stays on 15-year amortization, and mixed invoices need to be broken out. Coordinate the credit and the deduction. The 280C interaction and the new Form 6765 detail mean credit claims should be built alongside the return, not bolted on afterward.

The S-Corp R&D tax deduction rules for 2026 are genuinely favorable — immediate expensing is permanent, and the catch-up election recovers what the TCJA-era rules stranded. But the remaining window runs through this fall’s extended filing deadlines, and the elections are made on the return itself. This is one piece of the broader OBBBA picture for S-corp owners, and it moves your estimated tax planning too — a large 2025 deduction changes what you owe each quarter. If your S-Corp spent money on research or software development any time since 2022, contact us before the return goes out the door.