A coalition of decentralized finance (DeFi) builders led by Uniswap, Andreessen Horowitz (a16z) and Paradigm has filed a court brief backing the crypto industry's lawsuit against Illinois's 0.2% digital asset tax.

The group warns that the state's draft rules would convert fee-charging decentralized exchanges and their frontends into tax-collecting brokers — reviving a fight many in the industry believed had already been settled in Washington. In April 2025, Congress and President Donald Trump scrapped a federal IRS rule that would have required DeFi platforms to report user transactions as if they were brokers.

Who signed the brief, and who else is involved?

The amicus brief — a court filing by non-parties to a case who want to offer arguments or expertise — was filed in the Circuit Court of Sangamon County in support of a challenge brought by the Crypto Council for Innovation (CCI) and the Blockchain Association.

In addition to the DeFi Education Fund, a16z, Paradigm and Uniswap, the signatories include Aave Labs, Aptos Labs, Aztec Labs, Chainlink Labs, Jito Labs, Orca Creative, Phantom Technologies, Multicoin Capital, the Solana Policy Institute and Stand With Crypto.

The industry effort also has support at the federal level. According to the Blockchain Association, the US Department of Justice filed a statement of interest on November 6, arguing the tax "undermines federal policy and American leadership in digital assets."

The US Chamber of Commerce and the Securities Industry and Financial Markets Association (SIFMA) filed their own amicus brief the same day. The association warned that the levy would extend beyond crypto-native firms to banks, broker-dealers and custodians that offer digital asset products.

Why builders say a DEX cannot collect tax

Miles Jennings, a16z's head of policy, publicly addressed the matter on October 30, when he said his organization, the DeFi Education Fund and Uniswap were joining the fight against the tax act. He argued that the state's approach is impossible to comply with, because "autonomous software is not a person that can collect a tax."

The signatories also flagged a draft provision, noted in an October letter, that would require brokers to store customers' private keys. They say the requirement would expose users to theft and have asked regulators to replace the term with "public keys."

When the tax was signed, and who is fighting it

Governor JB Pritzker signed the measure as the Illinois Digital Asset Tax Act in June 2026 as part of the state's fiscal 2027 budget. It imposes a 0.2% charge on the value of a digital asset each time an Illinois customer exchanges, transfers or stores it through a broker.

The charge applies even when the customer makes no sale or gain, and noncompliance carries a class 3 felony penalty — a category punishable in Illinois by two to five years in prison.

Stakeholders have since taken the state to court over the law. The Digital Chamber was first, suing in July, while CCI and the Blockchain Association followed in September. In October, the state agreed to delay the tax's start from January 1, 2027, to July 1, 2027, while the litigation proceeds.

Where the federal DeFi broker rule came from

In December 2024, under the Biden administration, the Treasury Department finalized a rule that would have required platforms facilitating digital asset transactions to file Form 1099-DA on user activity. The so-called DeFi broker rule was set to take effect in 2027.

It will not take effect by that date: President Trump killed the rule when he signed a congressional review act resolution — a mechanism that lets Congress void recently finalized federal regulations by simple majority vote — on April 10, 2025.

The Illinois dispute will now test whether the state can prevail where the federal government reversed course — or whether the industry can wave off a state rule that challenges the way decentralized exchanges currently operate.