Fundamentals · Guide · Working level
The specialty-tax calendar: deadlines that cannot be fixed later
A quarter-by-quarter planning calendar for a business using the research credit, Section 174A expensing, cost segregation, and estimated taxes — organized around the elections that die if missed: the payroll offset, partial dispositions, and Form 3115 windows.
For a business using the research credit, Section 174A expensing, and cost segregation, the tax year is not one deadline in April — it is a chain of elections, several of which cannot be made late, fixed by amendment, or bought back at any price. The three that kill the most value when missed: the payroll-tax offset election (original timely return only), the partial disposition election (year-of-disposition return only), and the Form 3115 filing window (closes when the return is filed).
The organizing principle of this calendar is simple: extend the return, and work backward from the elections that die.
What can never be fixed later
Before the calendar, the triage. Specialty-tax items fall into three bins:
Fixable anytime the statute is open — the research credit itself (claimable by amended return within the refund limitations period, with heightened documentation for refund claims), and most missed depreciation.
Fixable only by method change — depreciation errors two or more years old, including adopting a cost segregation study on a prior-year building, which requires Form 3115 rather than amendment (see Pub 946 on depreciation and Pub 538 on methods).
Not fixable at all — the elections below. These drive the calendar.
| Election | Deadline | If missed |
|---|---|---|
| §41(h) payroll-tax offset (Form 6765, Section D) | Original return, timely filed incl. extension | Lost for the year; credit becomes carryforward only |
| Partial disposition (Treas. Reg. §1.168(i)-8(d)) | Return for the year of disposition, incl. extension | Remaining basis stays buried in the building; later recovery only via a narrower method change |
| Form 3115 automatic change (original copy) | Attached to timely filed return for year of change | Wait a year; eligibility rules may have changed |
| §280C(c) reduced-credit election | Original return, timely filed incl. extension | Full credit with the deduction disallowance — sometimes worse after modeling |
| Bonus depreciation election out (Form 4562) | Timely filed return incl. extension | Bonus applies by default to the class |
Q1 (January–March): close the prior year deliberately
- January: Deliver the R&D credit study data request while engineers still remember the year. Reconcile Section 174A domestic R&E expensing against the credit's QRE base — the populations overlap but are not identical, and inconsistency between them is an examiner's first question.
- By March 15 / April 15: File extensions for passthroughs and corporations as a matter of policy, not slippage. The extension is what keeps every election in the table above alive until September or October.
- Q1 estimate (April 15 for calendar-year corporations): First-quarter estimates should already reflect Section 174A expensing and any bonus depreciation on property acquired after January 19, 2025 — overpaying estimates all year to "be safe" is an interest-free loan.
- Fix the payroll offset now, not at filing: a qualified small business (under $5 million in gross receipts, within its first five gross-receipts years) that wants the offset must plan the Form 8974 mechanics with its payroll provider — the offset starts on the first Form 941 filed after the income tax return claiming it.
Q2 (April–June): construction, disposition, and the June estimate
- Cost segregation on current construction: Engage studies for buildings placed in service this year before year-end books close; the study also feeds the Q3–Q4 estimates. For renovations, flag every component removed — each ripped-out roof, HVAC unit, or facade is a partial disposition whose election belongs on this year's return and nowhere else.
- June 15: Q2 estimate. By now the prior-year credit study should have a working number; true up.
- Energy incentives with terminal dates: Section 179D is gone for property whose construction begins after June 30, 2026, and Section 45L for homes acquired after that date — projects straddling the line needed construction-start or acquisition documentation locked in Q2 of 2026. Prevailing wage and apprenticeship records must be contemporaneous; they cannot be reconstructed.
Q3 (July–September): file the passthroughs, land the elections
- September 15: Extended passthrough returns. This is the real deadline for partnerships and S corporations for the payroll-offset election (via Form 6765), 280C, bonus elections on Form 4562, partial dispositions, and the original Form 3115 copy for the year of change.
- Superseding-return window: A return filed before the extended due date can be superseded — replaced outright — until that date. An error caught in August on a July-filed return is fixable as if it never happened. This is the second reason to extend even when the return is ready in spring.
- September 15 estimate: Q3 payment, now with near-final credit and depreciation numbers.
Q4 (October–December): file the corporations, then plan forward
- October 15: Extended C corporation returns — same election checklist as September.
- October–November: Next-year planning. Model the Section 38(c) limitation before assuming the credit is usable (see the general business credit limitation); decide whether next year is a payroll-offset year; screen any contemplated equity transactions for Section 382/383 exposure.
- December: Place-in-service pushes. Property must be placed in service — not merely paid for — by year-end to depreciate this year. Acquisition-date documentation matters again for the bonus regime split at January 19, 2025.
- December 31: Last day to trigger (or defer) partial dispositions and to complete any acquisition intended for this year's cost segregation.
The full calendar, one table
Every date below assumes a calendar-year taxpayer; fiscal-year filers shift accordingly.
| Date | Item | Fixable later? |
|---|---|---|
| Jan 31 | Q4 Form 941 (payroll offset flows here if elected last year) | Amendable |
| Mar 15 | Passthrough returns or extensions | Extend — always |
| Apr 15 | C corp returns or extensions; Q1 estimate | Extend — always |
| Jun 15 | Q2 estimate | Penalty only |
| Jun 30, 2026 | 179D construction-start / 45L acquisition terminal date | No |
| Sep 15 | Extended passthroughs: payroll offset, 280C, partial dispositions, 3115, bonus elections | No (elections) |
| Sep 15 | Q3 estimate | Penalty only |
| Oct 15 | Extended C corps: same election set | No (elections) |
| Dec 31 | Placed-in-service cutoff; disposition timing | No |
| Rolling | Refund-claim statute (generally 3 years from filing) for amended-return credits | Until it closes |
When this calendar is overkill
A business with no current-year building activity, no qualified-small-business status, and a mature, stable R&D credit can run a lighter version: extend, file, done. The calendar earns its keep in transition years — first credit year, first building, first profitable year, an acquisition — when three or four irrevocable elections land in the same filing season. Those are also the years when a specialty provider's deliverable schedule must be contractually tied to your filing dates, not theirs. A study delivered October 20 is a study delivered next year.
Frequently asked questions
- Can the R&D payroll tax offset election be made on an amended return?
- No, with one narrow historical exception. The Section 41(h) payroll offset election must be made on a timely filed original return, including extensions, with Form 6765 attached. Miss the filing and the election is gone for that year — the credit survives as an income-tax credit carryforward, but the payroll-offset cash does not. This is the single strongest argument for extending the return of any qualified small business.
- When must a partial disposition election be made?
- On a timely filed original return, including extensions, for the tax year in which the building component is disposed of. Rip out a roof in 2026 and the election to deduct its remaining basis belongs on the 2026 return; by the 2027 filing season the ordinary election is dead, and recovering it later requires an accounting method change with much less flexibility.
- Does extending a business tax return increase audit risk?
- There is no credible evidence that extensions increase examination rates, and the IRS selects returns on content, not filing date. For a business using specialty incentives, the extension is affirmatively valuable: it keeps the payroll-offset election, partial disposition elections, Form 3115 filings, and superseding-return corrections alive for six additional months.
- When is Form 3115 due for an automatic accounting method change?
- The original Form 3115 attaches to the timely filed federal return, including extensions, for the year of change, with a duplicate copy filed with the IRS in Ogden no earlier than the first day of the year of change and no later than the original is filed. For a calendar-year business on extension, that window effectively runs through October 15 of the following year.