Tax Law Updates and Effective Dates
The dates that matter most for current cost segregation work, as of October 16, 2026: 100 percent bonus depreciation after January 19, 2025, 2026 §179 limits, Form 3115 list dates, and the construction and placed-in-service windows for qualified production property.
Educational information, not tax advice.
Updated 2026-10-14
Key takeaways
- Public Law 119-21, enacted July 4, 2025, restored 100% bonus depreciation for qualified property acquired after January 19, 2025 (as of October 16, 2026).
- Binding-contract property stays on the prior phase-down: 40% for 2025 placements, 20% for 2026.
- For tax years beginning in 2026, the §179 limit is $2,560,000, phasing out above $4,090,000 (Rev. Proc. 2025-32).
- §168(n) qualified production property is elective, temporary, and covered by interim Notice 2026-16. No eligibility conclusions are reached here.
- The Cost Segregation Audit Techniques Guide (February 2025) predates the 2025 law and is not authority.
Depreciation rules change by statute and by IRS guidance, often with different acquisition dates and placed-in-service dates. Publishing an old bonus percentage as current law is a common error. This page records the dates verified for CostSeg SI’s research register as of October 16, 2026. Educational information, not tax advice.
Public Law 119-21, §70301, makes the additional first-year depreciation allowance 100 percent for qualified property acquired after January 19, 2025. Property acquired under a written binding contract before January 20, 2025 stays on the prior phase-down (40 percent for 2025 placements, 20 percent for 2026). Notice 2026-11, announced January 14, 2026 (IR-2026-06), is interim guidance. Proposed regulations (RIN 1545-BR95) had not been published when this page was written.
The official title of Public Law 119-21 is the reconciliation act enacted July 4, 2025. The IRS describes the law as commonly known as the One, Big, Beautiful Bill Act. Website copy follows that IRS phrasing rather than presenting the short title as the official name.
Section 179 limits and qualified production property have their own effective dates, listed below. Form 3115 automatic-change lists also move by filing date. A study completed in 2026 still uses the law that applied to the original acquisition and placed-in-service dates for look-back components.
This page does not replace a CPA’s check for guidance issued after October 16, 2026. Time-sensitive figures should be re-verified before a return is filed.
Bonus depreciation timeline
September 27 and 28, 2017: the prior 100 percent bonus cutoff for property acquired after September 27, 2017, under the law commonly known as the Tax Cuts and Jobs Act (Public Law 115-97, enacted December 22, 2017). Notice 2026-11 still uses those dates for the phase-down group.
2023 through 2026 phase-down for that pre-January 20, 2025 group: 80 percent, 60 percent, 40 percent, and 20 percent by placed-in-service year, with long-production-period property and certain aircraft lagging one year. Rev. Proc. 2026-15 states that this group placed in service in calendar year 2026 gets 20 percent.
January 19 and 20, 2025: the new acquisition cutoff. July 4, 2025: enactment of Public Law 119-21. For the first taxable year ending after January 19, 2025, a taxpayer may elect 40 percent (60 percent for specified long-production property and aircraft) instead of 100 percent. That election does not last into later years.
Section 179 and QPP dates
Public Law 119-21 §70306 raised the §179 statutory limit to $2,500,000 and the phase-out threshold to $4,000,000 for property placed in service in taxable years beginning after December 31, 2024. Rev. Proc. 2025-32, released October 9, 2025, sets tax-year-2026 figures at $2,560,000 and $4,090,000, with a $32,000 SUV cap. Publication 946 lists $31,300 as the 2025 SUV cap.
Section 168(n) applies to property placed in service after July 4, 2025. Construction must begin after January 19, 2025 and before January 1, 2029. The property must be placed in service in the United States or a possession before January 1, 2031. The allowance is elective and temporary. Notice 2026-16 is interim guidance. This page does not decide that any reader’s building is qualified production property.
Office, administrative, lodging, parking, sales, research, software-development, and engineering space is excluded from QPP under the statute as summarized in the research register and IRS newsroom materials. A 10-year recapture period applies if use changes. Discuss any election with a CPA.
Forms, publications, and method-change dates
Rev. Proc. 2025-23 is the current automatic-change list, effective for a Form 3115 filed on or after June 9, 2025. Rev. Proc. 2026-32 modifies sections of that list for a Form 3115 filed after September 4, 2026. The Form 3115 instructions revision is December 2022. Designated change numbers can move when a successor list is issued.
The 2025 Instructions for Form 4562 describe the restored bonus allowance, the 40 percent / 60 percent election, QPP, and the removal of certain solar and wind energy property from the 5-year class for construction beginning after December 31, 2024. Publication 946 (2025) and Publication 527 (2025) are the current IRS plain-language editions as of October 16, 2026. No 2026 edition of Publication 946 was found.
Publication 5653, the Cost Segregation Audit Techniques Guide, was revised February 2025. It predates Public Law 119-21. It remains examiner guidance and cannot be cited as authority. Its bonus-rate discussion is out of date.
How to read dates on this site
Every bonus percentage and every §179 dollar figure on CostSeg SI pages should carry an as-of date and the tax year. If a page states 100 percent without “acquired after January 19, 2025” and an as-of date, treat that page as incomplete.
Look-back studies use the original acquisition and placed-in-service dates. A 2026 study of a 2020 building does not import the 2025-law 100 percent rate onto those old components.
State conformity is a separate calendar. California’s FTB 3885 instructions conform to the Code as of January 1, 2025 and do not include Public Law 119-21. Other states are not listed on this page. Super Intelligence is proposed documentation support, not a live update service.
Sources
- 1Public Law 119-21 (July 4, 2025), §§70301, 70306, 70307(opens in a new tab)
The 2025 reconciliation law, which the IRS describes as commonly known as the One, Big, Beautiful Bill Act.
- 2
- 3
- 4
- 5IRS Publication 946 — How To Depreciate Property (2025)(opens in a new tab)
Appendix B reproduces the Rev. Proc. 87-56 class lives.
- 6IRS Publication 5653 — Cost Segregation Audit Techniques Guide (rev. 2-2025)(opens in a new tab)
Written for IRS examiners. The guide states it is not an official pronouncement of law and cannot be cited as authority. It predates the July 2025 law.