With Governor Parson set to decide whether to raise Missouri’s gas tax in the coming days, the general assembly’s decision to sidestep voter approval on the issue has reignited discussion about the state’s consequential Hancock Amendment.

In 1980, Missouri voters approved an amendment to the state’s constitution adding Article X, Sections 16 through 24, which are collectively referred to as the Hancock Amendment. The sections are some of Missouri’s most important safeguards against higher taxes and growing government. But as with most constitutional topics, the Hancock Amendment and its implications are quite complex.

The concerns about this year’s gas tax bill center around Article X, Section 18(e) of Missouri’s constitution, which was approved in 1996. The subsection states that in addition to the other limitations imposed by the Hancock Amendment, Missouri’s general assembly cannot raise taxes or fees above a certain threshold in a given year without voter approval.

To avoid a public vote, the cumulative revenue impact of every bill passed by the legislature each year must be calculated and determined to be below the constitutionally defined limit. If the limit is exceeded, the bills that raise revenue must be submitted for a public vote starting with the largest increase, then every other increase in descending order, until the net effect of the remaining bills is lower than the year’s cap.

Here’s an example. Let’s say the cap in a given year is $100 million, and the legislature has enacted net tax increases of $125 million, and the most expensive bill raises taxes by $30 million. You would only need to vote on that one bill. If the bill is rejected by voters, then the legislature is below the cap. If voters approve the bill, the bill no longer counts toward the Hancock cap. If one single bill didn’t cover the entire gap by itself, that’s where voting on each bill in descending order comes into play.

When the amendment was initially adopted, the cap was $50 million in new revenue but has since been adjusted according to state personal income growth, and for 2021 it was $111.8 million.

For this year’s gas tax bill, the official fiscal estimates suggest that once fully implemented, it could raise between $123–$455 million. On its own, the bill would appear likely to exceed the Hancock Amendment cap, but that’s only one part of the story.

First, since compliance with the amendment’s limit is based on the net effect of all legislative changes in a year, we can’t know whether there’s a violation until Governor Parson finishes signing this year’s bills. It is also important to remember that if one bill raises enough revenue to violate the amendment, as long as there’s another bill that would simultaneously lower taxes or fees such that the net tax increase is below the threshold, the general assembly could still avoid violating the constitution.

Second, the gas tax bill is really the first of its kind. There haven’t been similar past efforts to raise taxes the way it does while avoiding a public vote. The gas tax bill has a refund mechanism, which is explained in the first post in this series. Given the potential complexity of a refund, this part of the bill appears to serve as a tactic to avoid triggering the Hancock Amendment rather than an effort to ensure Missourians pay less tax. Consequently, there are a variety of unanswered questions about how a potential Hancock Amendment violation would be handled. (See here for further breakdown of the questions at hand.)

One thing we do know is that Missouri voters are all too familiar with being asked to raise the state’s gas tax, and since the last approved increase in 1997have shot down every one of them, including a vote in 2018. While we wait to see what’s decided on the topic, it’s fair to wonder whether the legislature’s choice to avoid a public vote will prove to be a wise one.