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With the R&D tax credit Deadline 2026 fast approaching, many businesses risk leaving money on the table simply because they are unaware of the key dates that apply to them.
In case you missed it, see our year-end webinar here for more detail on these changes within each of these areas.
The rest of this article applies specifically to important dates and deadlines related to the R&D tax Credit, as we enter the new calendar and tax years.
2026 (Tax Year 2025) Entity Filing Deadlines :
March 16th (Monday):
Partnerships – Form 1065
S Corporations – Form 1120-S
April 15th (Wednesday):
Individuals – Form 1040 including Schedule C
Corporations – Form 1120, Form 1120-F
Forms 7004, which enable returns to be filed on extension, must be filed by the entity’s applicable timely filing deadline listed above. Extensions push the original return due date by six months.
Amended Returns: Statute of Limitations
The R&D Credit can be claimed retroactively, up to three tax years prior, depending on past returns’ original filing dates and the statute of limitations. Currently, for example a company may be able to claim the credit as far back as tax year 2022, assuming it is a calendar-year filer.
Tax year 2022 (TY25 minus three years) will be used to illustrate the statute below:
If tax year 2022 was filed timely, by 3/15/2023, taxpayers have until 3/15/2026 to amend the entity return. This is even if the return was filed prior to the original filing deadline (in late February, for example).
If tax year 2022 was filed on extension, taxpayers have until the exact filing date of the original return, plus three years. A taxpayer whose extension pushed their original filing deadline to 9/15 of 2023, but filed the return on 8/15/2023, for example, would only have until 8/15/2026 to amend the tax year 2022 return.
Deadline to Amend 2022 – 2024 Returns without Capitalizing R&D Costs
Another major impact of the One Big Beautiful Bill (OBBB) and subsequent Rev Proc. 2025-28 was to allow for ‘retroactive relief’ of the previous requirement to capitalize domestic-based R&D costs.
See our past articles on the OBBB and Rev Proc. 2025-28 for more detailed guidance on these updates. Essentially, eligible small businesses can amend tax years 2022 – 2024 to claim the credit without capitalizing R&D costs. If R&D costs were capitalized on original returns, they can be amended to reinstate full expensing of such costs.
The deadline to amend these returns and avoid capitalizing R&D costs is 7/6/2026 for all tax years, 2022 – 2024.
There is no need to capitalize domestic R&D costs in tax years 2025 and onward, per the OBBB. For purposes of the retroactive relief, companies qualify as eligible small businesses if their average gross receipts from 2022–2024 are under $30M per year. If companies would rather forego amending returns, all remaining amortization expense of R&D costs can be accelerated:
100% in 2025
or 50%/50% in 2025/2026
These dates are extremely important, as companies can lose out on five to six-figure credit amounts that they are entitled to, simply due to missing an amendment deadline.
Leyton’s R&D Study Process and Why to File Timely
We always recommend that the R&D credit claim is included in a company’s original return filing, to avoid amendments and the associated costs and waiting period.
As the IRS’ workforce continues to decrease (25% just in calendar year 2025), the waiting period for amended returns processing and associated refunds can be several months to over a year.
To facilitate including the R&D Form in timely-filed returns, we recommend that the R&D study starts at least a month and a half prior to a company’s filing deadline in 2026.
The R&D study entails technical interviews, data gathering of both financial and technical support documents, and a thorough analysis of qualified costs and their nexus to qualified projects.
Leyton’s process also entails a detailed internal QC review & generation of a Technical Report, which serves to substantiate all activities and costs being qualified for the credit.
