Which States Index Their Gas Tax to Inflation? The Automatic Increase, Explained

Guides · October 9, 2026

On July 1, 2026, millions of drivers paid a little more at the pump and nobody in their state legislature voted for it. California's gas tax ticked up 2.2 cents. Maryland's rose 0.6 cents. Washington's went up 1.1 cents. These were not bills. They were formulas doing what formulas do. The states that index their gas tax to inflation have built a tax that raises itself, and the list is growing.

How the automatic increase works

Indexing ties the fuel tax rate to an economic measure so it moves without a vote. California's increase is tied to the California Consumer Price Index; the formula has run for about a decade, and this July it took the gas tax from 61.2 to 63.4 cents a gallon and the diesel tax from 46.6 to 48.2 cents. Maryland's is tied to the national CPI: over four years of elevated inflation from 2022 to 2026, the automatic mechanism pushed the rate from roughly 35 cents to 46 cents a gallon, a 30 percent increase that never appeared on a ballot. Washington just joined the club. A 2025 law raised its gas tax 6 cents and added annual inflation adjustments; the July 1 move to 56.5 cents was the first one.

The mechanism works both ways in theory. If the CPI fell, the indexed tax could fall too. In practice, sustained deflation is rare enough that drivers should not hold their breath. The ratchet moves one direction in real life.

Which states use indexing or automatic formulas

The July 1, 2026 round included California, Illinois, New Jersey, Maryland, Mississippi, and Washington, though not all of those are pure inflation indexing. Connecticut's diesel tax rose a cent to 49.9 cents under an annual pricing formula while its 25-cent gas tax has not moved since 2000. Nebraska, Pennsylvania, and West Virginia all have automatic adjustment formulas on the books, but their formulas did not trigger a change to start 2026, so their rates stayed flat. Florida, Georgia, Minnesota, and North Carolina saw small automatic increases of about a cent at the start of the year; New York, Utah, and Vermont actually ticked down slightly.

Michigan is the odd one out, and worth a paragraph on its own. It did not index. It restructured. A 2026 transportation package killed the 6 percent sales tax on fuel, much of which flowed to the general fund instead of roads, and replaced it with a higher fuel excise tax: 31 cents to 52.4 cents a gallon on January 1. Same pump pain, different plumbing, and now the money is constitutionally dedicated to transportation. It is not indexing, but it is the same underlying story: states are tired of fuel taxes that do not keep up.

Why states keep doing this

The case for indexing is arithmetic. Construction costs rise every year. The federal gas tax has been frozen at 18.4 cents since 1993, which is why the Highway Trust Fund keeps needing bailouts, and state legislatures do not want to repeat that mistake. Automatic adjustments give transportation departments predictable revenue without forcing lawmakers to cast a politically toxic vote every few years. Supporters say it keeps funding aligned with real-world costs.

Critics say that is exactly the problem. Automatic increases disconnect tax hikes from voter oversight. A tax that rises every year by formula never has to survive a debate, a committee hearing, or an election. It is taxation without representation-adjacent, and it lands hardest on people who drive for a living. For a trucker filling up daily, pennies per gallon compound fast: a 2-cent increase is real money across 100,000 miles a year.

Will more states join?

That is the open question, and the trend points one way. Automatic adjustments are becoming more common because they solve a real political problem for legislatures, and the states using them are not going back. The federal government shows the alternative: 33 years of a frozen rate and a trust fund that cannot pay its bills. But every automatic increase also feeds the argument that EV drivers, who pay no fuel tax at all, are getting the better deal, which is why 41 states now charge EV registration fees instead. Our EV fee guide covers that side of the same fight.

For drivers, the practical takeaway is simple. If you live in an indexed state, your gas tax will rise most years by a little, forever, and no election will change it. Budget accordingly, and check your state's rate each July. Our 2026 rate change roundup tracks the full list.