The Multi-State Inspection Matrix Dealerships Now Have to Run: EPA's Tier 4 Phase-In Delay and the Federal-State Divergence

A multi-state dealership group used to be able to print one delivery checklist and use it from Wichita to Worcester. After May 14, 2026, that is no longer true for model year 2027 and 2028 vehicles.

On that date EPA signed a Notice of Proposed Rulemaking that pushes the Tier 4 criteria-pollutant phase-in for light- and medium-duty vehicles from model year 2027 back to model year 2029. The proposal is titled “Revision of Tier 4 Criteria Pollutant Standards, Part 1: Amendments to Phase-In Schedule for Light-Duty and Medium-Duty Vehicles.” Manufacturers will keep building to Tier 3 for MY 2027 and MY 2028. The 45-day public comment period began on May 14. (EPA news release, May 14, 2026; EPA rule page.)

That sounds like a delay — fewer constraints, easier life. For dealerships and fleet operators delivering across state lines, the opposite is true. The federal delay does not move California. It does not move the 17 states plus the District of Columbia that have adopted parts of California’s Advanced Clean Cars II / LEV IV program under Section 177 of the Clean Air Act. Those states are still on the original schedule. So a single vehicle now sits in two regulatory universes at once, and the rule that controls is decided by where the customer registers it.

This is a compliance-matrix problem, not a paperwork problem. Below is what changed, who it lands on, and what a multi-state dealer or fleet compliance lead needs to set up before MY 2027 production hits the lot.

What the Delay Actually Says

The Tier 4 program — finalized as the “Multi-Pollutant Emissions Standards for Model Years 2027 and Later Light-Duty and Medium-Duty Vehicles,” 89 FR 27842 (April 18, 2024) — sets a fleet-average NMOG+NOx target of 15 mg/mi for light-duty vehicles by 2032 and 75 mg/mi for medium-duty vehicles by 2033. The standards are codified in 40 CFR Part 86. (89 FR 27842.)

The May 2026 NPRM does two specific things:

It moves the Tier 4 phase-in start from MY 2027 to MY 2029.
It announces a Part 2 rulemaking, not yet proposed, that will reconsider the long-term Tier 4 standards themselves.

It does not change Tier 3. It does not touch the nonroad Tier 4 program in 40 CFR Parts 1039, 1042, and 1054. It does not affect heavy-duty engine standards. And it does not pre-empt state authority under Sections 177 and 209 of the Clean Air Act.

EPA’s fact sheet (EPA-420-F-26-009) projects $1.7 billion in vehicle-cost savings during the delay window. The Regulatory Impact Analysis (EPA-420-D-26-001) was published the same day.

The Section 177 Map

Section 177 of the Clean Air Act, 42 U.S.C. § 7507, lets a state with a State Implementation Plan adopt California vehicle emission standards in lieu of federal standards. The standards must be identical to California’s, and the state must adopt them at least two years before the affected model year. (42 U.S.C. § 7507.)

California finalized Advanced Clean Cars II in 2022 with phase-in starting at MY 2026. The states that have adopted at least one ACC II program element fall into roughly two buckets (CARB published list):

Finalized for MY 2026 start — California, Massachusetts, New York, Oregon, Vermont, Virginia, Washington
Finalized for MY 2027 start — Colorado, Delaware, Maryland, New Jersey, New Mexico
Adopting at varying schedules — Connecticut, Maine, Minnesota, Rhode Island, plus the District of Columbia

The federal delay changes none of these dates. A vehicle delivered into Colorado for MY 2027 still has to meet Colorado’s adopted LEV IV standard. A vehicle delivered into New York still has to meet New York’s. The dealership’s home state of operation is not the controlling rule — the destination state is.

That is the divergence. From MY 2027 forward, a dealer group operating across the federal-state line is running two certification regimes at once, and will have to do so for at least two model years until federal Tier 4 catches up in MY 2029.

What a Multi-State Dealership Actually Has to Manage

The delivery line is where the matrix lives. Here is what changes:

Certification labels. Every new motor vehicle bears a Vehicle Emission Control Information label under 40 CFR 86.1807-01 that identifies the certification family and applicable standards. A federally certified Tier 3 vehicle and a California-certified LEV IV vehicle have different VECI labels. Dealers in Section 177 states must confirm the label corresponds to that state’s requirements before delivery, not after.

Section 203 exposure. 42 U.S.C. § 7522 — Clean Air Act Section 203 — prohibits the sale or offer for sale of any new motor vehicle not covered by a valid certificate of conformity for that vehicle. Selling a federally certified vehicle into a Section 177 state where the certificate of conformity does not satisfy the state’s adopted standards puts the dealer in Section 203 territory, not just the manufacturer. (42 U.S.C. § 7522.)

Title and registration. Most Section 177 states condition title issuance on California-style certification documentation. A vehicle that delivers on Friday and fails to title on Monday is the dealer’s problem to unwind, not the manufacturer’s.

Customer disclosure across state lines. Border markets — Kansas City, St. Louis, Texarkana, Memphis, Omaha — routinely deliver vehicles to customers who will register in another state. The destination state controls. The customer who walks onto a Missouri lot but registers in Illinois (not Section 177) and the customer who walks onto a Missouri lot and registers in New York (Section 177) leave the same dealership with different compliance pictures attached to the sale.

The OBD layer. Section 177 states’ I/M programs increasingly verify OBD readiness against the standard the vehicle was certified to. A federally certified MY 2027 Tier 3 vehicle running into a Colorado AIR Care or Washington emissions check, two model years later, may not look the way the local I/M station expects.

Recordkeeping. Retain the VECI label photo, the certificate of conformity copy, the destination state, and the customer registration address on every vehicle file. Clean Air Act recordkeeping violations are currently assessed at up to $45,268 per day per violation under the January 2025 inflation adjustment to 40 CFR Part 19. (2025 inflation adjustment.)

The Penalty Math

Section 205 of the Clean Air Act, as inflation-adjusted in January 2025, sets the following maximums for mobile-source violations (40 CFR Part 19):

$45,268 per noncompliant vehicle or engine sold or offered for sale
$4,527 per tampering event or sale of a defeat device
$45,268 per day for recordkeeping and reporting violations

That first number — $45,268 per vehicle — is the one that scales fast for a dealer group. A regional OEM network making 50 deliveries per quarter into a Section 177 state without the right certification is staring at a theoretical $2.26 million quarterly exposure under Section 205 alone, before the state’s parallel claim under its own adopted standards.

EPA mobile-source enforcement has historically reserved the per-vehicle penalty for import-and-resale operators and defeat-device cases. Whether the agency expands its use against franchised dealers in the Section 177 delivery window is open. The state side, however, does not need EPA to act. CARB and the ACC II states have independent enforcement authority under Section 209 and can pursue noncompliant deliveries directly. (EPA Clean Air Act Mobile Source Civil Penalty Policy.)

Where I/M Programs Sit in the Picture

State Inspection / Maintenance programs are a second tier on top of the new-vehicle question. A vehicle that arrives in an I/M jurisdiction has to be able to pass that jurisdiction’s protocol — which, in adopting states, is keyed to the standard the vehicle was certified to.

For dealers operating in the central United States, the I/M map is uneven:

Missouri runs the Gateway Vehicle Inspection Program in the St. Louis metro (Franklin, Jefferson, St. Charles, and St. Louis counties, plus St. Louis City). Statewide safety inspections at Missouri State Highway Patrol-authorized MVI stations apply to vehicles older than 10 years or over 150,000 miles, biennially. Most new-car dealers operate as MVI stations. (MSHP MVI program.)
Texas runs emissions inspections in 17 designated counties around Houston, Dallas, Austin, El Paso, and Fort Worth. Bexar County (San Antonio) phases in during 2026. Senate Bill 1448 eliminated statewide passenger safety inspections effective January 1, 2025; commercial vehicles, salvage-title vehicles, and certain teen-driver vehicles remain in the program. (TCEQ I/M overview; Texas DPS announcement.)
Kansas, Oklahoma, Arkansas, Nebraska, and Kentucky have no statewide I/M program. Federal new-vehicle standards control without a state-side overlay.
Section 177 states maintain their own I/M programs keyed to their adopted standards. A dealer who delivers into Colorado, Washington, or New York is delivering into a closed regulatory loop where the new-vehicle certification and the I/M protocol both reference the state-adopted rule, not the federal one.

None of the central states are Section 177 states. A dealership group whose footprint is entirely Missouri / Kansas / Oklahoma / Texas can run a single federal-Tier-3 protocol through MY 2028. The moment that group adds a Colorado or Washington store — or starts cross-shipping vehicles to a partner network — the matrix is live.

What the Compliance File Needs to Look Like

A dealer compliance lead managing this divergence should expect to maintain, for each vehicle, the following at delivery:

The VECI label photo and a record of which certification family it identifies
The certificate of conformity reference for that family
The buyer’s registration state
A flag (yes / no) for whether the registration state has adopted ACC II / LEV IV for that model year
A second flag for whether the destination state’s I/M program is active in the buyer’s county
The dealer-side disclosure given to the buyer if the destination state has a different applicable standard than the certification family

That file is what gets pulled in a Section 203 audit, in a state DMV registration dispute, or in a Section 205 enforcement notice. Holding it together across a multi-store group requires a single compliance owner, not a per-store policy.

The Litigation Watch

EPA’s May 2026 proposal is not yet final. The 45-day comment period ends in late June 2026. Two recent multistate suits — the 10-state PM2.5 NAAQS designation suit filed in N.D. Cal. in May 2026, and the 25-state endangerment-finding rollback suit filed in March 2026 — show the same coalition is positioned to challenge the Tier 4 delay when and if it finalizes. A Tier 4-specific suit has not been filed as of mid-May 2026.

The dealer-side implication: do not plan delivery operations on the assumption the delay will survive intact. The Section 177 schedule is not contingent on EPA’s federal schedule and will not move regardless of how the litigation resolves. The matrix exists either way.

What This Costs to Get Right

A multi-state dealer group can build the matrix two ways. The first is to hire a full-time mobile-source compliance manager — a credentialed environmental specialist with EPA mobile-source program experience and ACC II familiarity. In most regional markets that is a $95,000 to $140,000 fully loaded position, plus the cost of standing up the certification-tracking workflow.

The second is to attach the function to an outside compliance program for a fraction of that cost — typically structured as a retainer that covers monthly certification matrix review, state-adoption tracking, recordkeeping audit, and customer-disclosure language across the dealer group’s footprint. iSi Environmental’s EHS COOP retainer is built for exactly this pattern: clients access a compliance lead and the underlying regulatory specialists on a fixed monthly fee instead of a full-time hire, and the program scales across multiple sites under one engagement. For a dealer group running between two and ten stores, the retainer typically runs in the low five figures monthly — a fraction of the full-time-hire cost while covering more states and more rule sets than a single internal hire can credibly track.

The Tier 4 phase-in delay is a clear example of why dealer compliance is no longer a single-state function. The May 14 NPRM creates two parallel rule sets — federal Tier 3 through MY 2028 and California LEV IV starting at MY 2026 — and lets each state pick which one applies inside its borders. A dealer group either builds the matrix or absorbs the per-vehicle exposure when the matrix breaks.

The federal delay was sold as relief. For multi-state dealerships, it is the opposite. The compliance work the industry was asked to do under one rule has been replaced with the work of running two rules simultaneously, and the dealer is the one closing the gap at the point of sale.

iSi Environmental builds compliance programs for fleet operators, dealer groups, and multi-site clients across the central United States. The firm’s environmental compliance retainer covers mobile-source rule tracking, recordkeeping audits, and state-by-state certification matrix maintenance — the work most often missed when a regulation splits federal and state schedules. Contact iSi for a compliance review of your current dealer or fleet operations.