Income Tax Conformity – The History, The Process & Why It All Matters

Every year the Arizona State Senate and House of Representatives must consider whether or not and how to conform to the Internal Revenue Code (IRC) for the tax year that just ended. To Arizona taxpayers this is vitally important since they must use federal adjusted gross income to determine the starting point for filing state tax returns. With the legislative session convening in January and tax returns due April 15, the pressure is on to pass the conforming legislation early. Without early passage, taxpayers and tax preparers are left making assumptions and often file for extensions or have to amend returns. When conformity occurs late in the session it means higher costs to the taxpayer and more complexity and time spent on state income taxes.

So why does the Arizona Legislature have to consider this bill each year? Rather than create a separate tax code with separate definitions, Arizona uses the IRC as the base for the state, making taxes less complicated for taxpayers. Since state returns use the federal definitions as the starting point, any changes at the federal level mean Arizona needs to update, or taxpayers face increased complexity and higher likelihood of amended returns or errors.

It turns out the Arizona Constitution prohibits the delegation of legislative authority, meaning state legislators can’t designate the IRC as the definition for Arizona taxes on a rolling basis, automatically adopting any changes made at the federal level. Instead, the state uses fixed date conformity, which aligns Arizona taxes to the IRC as of a specific date in time and allows lawmakers the ability to assess federal changes each year. 

That hasn’t always been the case. Prior to 1980 Arizona did not conform to the IRC at all, and instead made its own definitions of what was taxable at the state level. That meant individuals and businesses had to keep federal and state definitions in mind when filing both returns, making the filing process a laborious one. To simplify the process and ease the burden on taxpayers, Arizona began conforming on a fixed date basis to the IRC. 

In most years income tax conformity is noncontroversial and viewed as a technical exercise, updating the date in Arizona Revised Statute that refers to the IRC. When Congress enacts major changes or overhauls, like with the Tax Cuts and Jobs Act of 2017, there are potential revenue impacts in Arizona. In those instances, the process of conforming can become more complex and delve more into policy considerations, often delaying legislative resolution and thereby causing uncertainty for Arizona taxpayers. 

ASCPA members and tax experts David Walser, Anne Cornelius, Ed Zollars and Jared Van Arsdale provide insights on income tax conformity and why it matters to Arizonans. Longtime ASCPA lobbyist Kevin DeMenna shares historical context and the politics behind this annual exercise. Arizona Department of Revenue Deputy Director Dr. Grant Nülle gives an overview of the process from the department’s perspective.