Four States, Four Ways to Conform: CO, AZ, IA, MT and OBBBA

When Congress passed the OBBBA in July 2025, it created a federal tips deduction worth up to $25,000 per year. But whether that deduction also reduces state income tax depends entirely on how each state connects to the Internal Revenue Code. Colorado, Arizona, Iowa, and Montana all honor the deduction, but they arrive at that answer through four distinct mechanisms. For tipped workers choosing where to live or simply trying to understand their state return, those differences matter.

Four different conformity mechanisms

States connect to the federal tax code in different ways. Some start their tax calculation from federal taxable income, inheriting all federal deductions automatically. Others start from federal AGI or their own definition of income, requiring explicit legislative action to adopt new federal deductions. Here is how these four states handle it:

• Colorado: Structural flow-through from federal taxable income (4% flat rate)
• Arizona: SB 1171 IRC adoption (3% flat rate)
• Iowa: Explicit DOR guidance plus structural flow-through (4% flat rate)
• Montana: Federal taxable income base (5%/6% graduated rates)

Colorado: structural flow-through

Colorado computes state income tax by applying its flat 4% rate directly to federal taxable income. This is the simplest conformity mechanism. Because the OBBBA tips deduction reduces federal taxable income (it is an above-the-line deduction that flows through to Form 1040 Line 15), the reduced figure automatically becomes the Colorado tax base. No separate Colorado legislation was needed, and the Colorado DOR has confirmed the flow-through.

This structural approach means Colorado will automatically adopt any future federal above-the-line deduction that reduces federal taxable income, unless the state legislature explicitly decouples. For tipped workers, the benefit is immediate and requires no special action on the state return.

Arizona: SB 1171 IRC adoption

Arizona takes a different path. The state adopted the Internal Revenue Code as amended through early 2026 via SB 1171 (2025 legislative session). This legislative action explicitly brought the OBBBA into Arizona's tax framework. Arizona uses federal AGI as its starting point with Arizona-specific modifications, so the OBBBA tips deduction (which reduces federal AGI) flows through to reduce Arizona taxable income.

The Arizona DOR confirmed the conformity. At the state's flat 3% rate, a worker deducting $20,000 in tips saves $500 in Arizona state tax. Arizona's rate is one of the lowest flat rates in the country, but the savings are additive with the federal deduction.

Iowa: explicit DOR guidance + structural

Iowa provides what might be called a "belt and suspenders" answer. The state conforms through two independent mechanisms. First, Iowa's IA 1040 starts from federal taxable income (Line 02 equals federal Form 1040 Line 15), so the OBBBA deduction structurally flows through. Second, the Iowa DOR published explicit guidance confirming that qualified tip income is not subject to Iowa income tax under the OBBBA.

Either mechanism alone would be sufficient, but having both provides the strongest possible confirmation. At Iowa's flat 4% rate, a worker deducting $20,000 in tips saves $760 in Iowa state tax.

Montana: federal taxable income base

Montana, like Colorado, starts from federal taxable income as its computation base. The OBBBA tips deduction reduces federal taxable income, and that reduced figure flows into Montana's tax calculation. However, Montana differs from the other three states in two important ways: it uses a graduated rate structure and applies its own standard deduction and personal exemption on top.

Montana's 2026 brackets are 5% on income up to $21,600 (single) and 6% above that. The state also applies its own standard deduction of $5,540 and a personal exemption of $3,000. Because the tips deduction has already reduced the federal taxable income starting point, the Montana deductions are applied to a smaller base, and the graduated rates determine the actual savings.

Worked example: $20,000 tips in each state

Why the mechanism matters

For a tipped worker filing a 2026 return, the practical outcome is the same in all four states: the tips deduction reduces your state tax. But the mechanism matters for durability and predictability.

• Structural flow-through (Colorado, Iowa, Montana) is the most durable. Because the state tax base is defined as federal taxable income, any future federal deduction automatically flows through without new state legislation. The state would need to actively decouple to block a federal provision.
• Legislative IRC adoption (Arizona) depends on the legislature periodically updating the conformity date. If Arizona's legislature fails to pass a future conformity bill, the state could fall behind the IRC and stop recognizing new federal provisions.
• Explicit DOR guidance (Iowa) provides administrative certainty. Even if there were ambiguity in the structural mechanism, the published DOR guidance eliminates doubt. This is especially valuable during the first filing season after a major federal tax change.

Workers in non-conforming states like New Jersey, Massachusetts, Kentucky, and Minnesota do not receive any state-level benefit from the OBBBA tips deduction. Wisconsin also does not conform after the governor vetoed tips and overtime bills. Michigan and Indiana have since confirmed conformity through their own mechanisms - see our updated conformity tracker for details. The gap between conforming and non-conforming states can add hundreds or thousands of dollars to a tipped worker's annual state tax bill.

For the complete state-by-state breakdown, see our state tips and overtime taxes map. You can also estimate your take-home pay using the Colorado,Arizona,Iowa, or Montana paycheck calculators.