Federal Tax Reform State Conformity Issues for Business Filers

Federal tax reform has become a state-by-state calculation problem for business filers. The OBBBA’s mid-fiscal-year enactment triggered divergent state responses that make federal taxable income an unreliable guide to state obligations on its own. Businesses need to check each provision in every jurisdiction where they file and use the results for estimated payments, owner-level planning and financial reporting before they prepare their returns.

Why the OBBBA's July 4 enactment created a state conformity problem that business filers cannot ignore

The OBBBA was signed July 4, 2025, with many provisions effective January 1, 2026, creating a mid-fiscal-year problem for states. Legislatures had less time to respond than a January enactment would have allowed. EY’s Scott Roberti identified the central pressure as the need to act or absorb unexpected revenue shortfalls. Because most states must maintain balanced budgets, federal deductions that shrink the state tax base are also budget decisions.

States build their income tax codes on the federal tax code, or IRC, and decide individually how closely to follow it. Federal relief thus leaves states to choose between a smaller tax base and different state rules that keep revenue from falling. The practical question for a business is not simply whether a federal deduction applies, but whether each state accepts it for the relevant year. That gap must be computed jurisdiction by jurisdiction.

How rolling, static, and selective conformity each respond to OBBBA — and where each type breaks down

A state’s conformity model establishes its default response, subject to subsequent changes in state law. Rolling conformity automatically incorporates IRC changes as enacted, so OBBBA provisions became state law on July 4, 2025, unless the legislature decoupled. Colorado was the first rolling conformity state to enact OBBBA legislation, illustrating how quickly the default can give way to a specific legislative response.

Static conformity instead follows the IRC as it existed on a fixed date. Federal amendments do not enter that framework until legislation advances the date or specifically adopts them. California illustrates the importance of the cutoff, because an update can still leave the state behind the federal law it appears to be addressing. Fixed-date states that updated early in 2025 may have locked in a pre-OBBBA version for the entire 2025 tax year, without a way to catch up until a later legislative session.

Selective conformity makes adoption a provision-by-provision decision from the outset. Alabama, Arkansas, Mississippi, and Pennsylvania use this model, under which OBBBA deductions generally require specific enabling legislation. Maryland demonstrates why the three categories are only a starting framework. Although technically a rolling state, its statute prevents automatic adoption of an IRC amendment affecting state income tax revenue by more than $5 million. In September, Maryland issued a formal report that named the OBBBA provisions lawmakers needed to act on.

The four federal provisions most likely to diverge at the state level and why each one creates its own compliance layer

States are most likely to differ from federal law on Section 174A R&E expensing, Section 163(j) interest limitations, Section 168(k) bonus depreciation, and Section 179 expensing. Each can reduce federal taxable income, creating revenue pressure for states that follow it. Their compliance effects differ, however, because they affect different deductions, schedules and carryovers. A single federal-to-state adjustment cannot capture all four.

The OBBBA’s new Section 174A under P.L. 119-21 restores immediate expensing of domestic research and experimental expenditures, reversing the TCJA’s capitalization requirement. State resistance can therefore separate the timing of the state deduction from the federal deduction. Michigan and Pennsylvania have rejected the new domestic R&E treatment. The less obvious complication is retroactivity. For businesses with significant R&E expenses, conformity issues may affect 2025 returns and reach back to tax years 2022–2024.

Section 163(j) creates a different layer by restoring adjusted taxable income, or ATI, to an EBITDA definition. Compared with the EBIT standard that had applied, this generally permits larger federal interest deductions. States adopted earlier versions of the limitation at different times and have responded inconsistently to subsequent changes, with Massachusetts delaying the OBBBA modification. Some states also decoupled from the 2019–2020 ATI increase. Those earlier differences leave state-only Section 163(j) carryovers that must be tracked separately from federal carryovers, so the current calculation cannot be understood without its history.

Section 168(k) bonus depreciation presents a more familiar divide, because many states have historically decoupled and that nonconformity is generally expected to continue. Businesses consequently need separate state depreciation schedules rather than assuming federal deductions determine state deductions. Delaware has decoupled from the enhanced rules, while Illinois has kept its broad Section 168(k) decoupling and has also rejected Section 168(n) bonus depreciation for qualified production property. The production-property provision covers nonresidential real property used in production activities under rules distinct from Section 168(k).

Section 179 adds another limit-based calculation. The OBBBA more than doubles the TCJA expensing limits, but states may retain their own annual limits and phaseout thresholds. Massachusetts, for example, temporarily delays the OBBBA version by retaining the TCJA version. A federal deduction can thus be larger than the state allows even when both systems allow immediate expensing. The common pattern is divergence, but the records needed to explain it depend on the provision.

What eight states have actually done — the legislative record through mid-2026

California’s senate bill 711, enacted October 2025, advanced its IRC conformity date to January 1, 2025. Because that date precedes OBBBA enactment, California follows no OBBBA provision by default. Its departures include Section 163(j), Section 174 treatment of domestic and foreign R&E, Section 168(k) bonus depreciation, and Section 179. The date update therefore did not bring the state into general alignment with the new federal law.

Illinois enacted SB 1911 on December 12, 2025, which blocked Section 168(n) bonus depreciation for manufacturers’ new assets and kept its existing Section 168(k) decoupling in place. The law also taxed a fixed share of overseas business profits regardless of whether the income was GILTI or NCTI. Its reach extends beyond the timing of deductions to the treatment of overseas income.

Michigan follows Sections 163(j), 174, and 179 as they existed under the TCJA and decouples entirely from Sections 168(n) and 174A. For tax years beginning after December 31, 2021, federal taxable income must be calculated as though the OBBBA transition rules do not apply. That scope makes the state’s response relevant to earlier years as well as current filings.

Indiana took a mixed approach in the conformity bill governor Mike Braun signed during a short legislative session. It temporarily coupled to federal tipped and overtime income deductions for 2026. It also permanently decoupled from Section 168(n) bonus depreciation for certain qualified production property.

Massachusetts enacted H.B. 5470 on June 12, 2026, with different timetables for different provisions. It follows TCJA treatment of Section 174 for 2025 and shifts to OBBBA treatment in 2026, rejecting Section 174A for 2025 but adopting it in 2026. It temporarily follows the TCJA version of Section 179 for 2025 and 2026. Conformity to the Section 163(j) modification is delayed until 2027.

Pennsylvania enacted legislation decoupling from domestic R&E expensing, interest expense limitations, and deductions for qualified production property. The measures save the state more than a billion dollars annually.

Oregon’s governor Tina Kotek signed legislation decoupling from the QSBS exclusion, bonus depreciation, and a deduction for car loan interest. By decoupling, the state keeps hundreds of millions of dollars in revenue over the 2025–27 budget cycle.

In the District of Columbia, the federal government can override decisions on conformity. D.C. had decoupled from overtime and tip exclusions and bonus depreciation despite using rolling conformity. Unlike the state legislative choices above, the federal override case shows that the landscape can shift even after a jurisdiction has acted.

How the PTET regime and SALT cap increase add a second conformity problem for pass-through entities and closely held businesses

For S corporations, partnerships and closely held businesses, provision-level conformity is only one layer. The OBBBA’s substantial increase in the federal SALT cap for most filers also changes the context for pass-through entity tax, or PTET, planning. The TCJA of 2017 capped the federal SALT deduction for itemized filers. Many states responded with PTET regimes allowing partnerships and S corporations to pay state income tax at the entity level, making it federally deductible and effectively bypassing the cap for owners.

The higher cap now raises a separate question about whether those regimes remain necessary or politically sustainable. Some states are actively reconsidering them, leaving uncertainty for businesses whose planning depends on PTET elections. Conformity differences also flow into individual owners’ state returns, compounding the burden for shareholders and partners filing in multiple states.

The retroactive R&E issue is especially consequential in that owner-level setting. Closely held businesses that did not expect back-year exposure may face conformity questions for 2022–2024 as well as current-year planning. The consequences must also be understood in the context of the owners’ returns and the PTET decisions built around them.

Where conformity uncertainty surfaces in financial reporting and what it means for ASC 740 disclosures

Uncertainty about conformity affects financial statements before tax returns are due. Under ASC 740 income tax accounting, deferred tax assets and liabilities must reflect each jurisdiction’s current law, even while future conformity decisions remain unresolved. How a business reports a pending bill therefore differs from how it reports a departure that has become law. Multi-state businesses may need jurisdiction-level models rather than a single calculation based on federal taxable income.

Timing makes that distinction harder to manage. States sometimes enact changes after a tax year closes or after returns have been filed, potentially requiring amended returns, refund claims or additional payments. A business may face a choice between filing under extension while awaiting legislation and filing on the original deadline with the risk of amendment. Neither route removes uncertainty around estimated payments or the ASC 740 footnote disclosures auditors must review.

Financial statement audits of multi-state businesses thus need to check state conformity positions as part of the deferred tax analysis. The additional scope is particularly significant where legislation remains pending. Tax return preparation and financial reporting cannot be treated as separate interpretations of the same law.

What proactive planning looks like when the conformity map is still being drawn

Begin with a state-by-state record of the major jurisdictions where the business operates. Identify each state’s rolling, static or selective model, then record its treatment of Sections 174A, 163(j), 168(k)/168(n), and 179. Keep the applicable tax year attached to each conclusion, because adoption can be delayed or temporary. Legislatures will keep working through 2026 and beyond, so this record needs to be checked and updated over time.

Use that record to recalculate estimated payments. Where a state rejects federal R&E expensing, bonus depreciation or the Section 163(j) EBITDA limit, state taxable income may be materially higher than federal taxable income. Payments calibrated only to the federal figure will then be underpaid. Businesses with significant R&E expenses should also check whether their state estimated payments for 2022–2024 were correct under the conformity rules each state used.

Where important legislation is still pending, consider filing under extension to allow time to use the law once it is enacted and avoid having to amend a return filed while the law was uncertain. Pass-through businesses should separately reassess PTET elections made under the old SALT cap logic. The higher federal cap may have materially changed the economics, while state reconsideration adds uncertainty about the regimes themselves.

Maintain contact with advisors during filing season and throughout the year. Mid-year changes can affect estimated payments, financial reporting and PTET elections on different timetables. For closely held and pass-through businesses, an advisory relationship that covers both tax and financial statement audit work closes the gap between the return and the ASC 740 footnote. The practical goal is one coordinated analysis that follows the law as it changes, before separate deadlines turn the same uncertainty into several problems.