Sen. Jon Kyl, R-Ariz., announced today he will resign from his appointed seat on Dec. 31, three days before the former lobbyist is required to file financial-disclosure paperwork.

Kyl had been working as a lobbyist when Arizona Gov. Doug Ducey appointed him to fill the late Sen. John McCain’s seat through 2020, but Kyl would only commit to serving through the end of the current congressional session.

The session officially closes on Jan. 3, the same day Kyl’s financial disclosure is due. Kyl was sworn in on Sept. 5 and filed for a 90-day extension to file his disclosure on Sept. 28, according to Senate records.

A spokeswoman for Kyl’s office had not returned an email about whether the senator would file his disclosure before leaving office by the time of publication.

Since 2015, Kyl has been lobbying the federal government for Covington & Burling LLP, representing the pharmaceutical company Merck and Co., defense contractors Northrop Grumman Corp. and Raytheon Co., Walmart Inc., the telecommunications company Qualcomm Inc., and the conservative group Judicial Crisis Network, among other clients.

The Arizona Republic reported today that it wasn’t clear whether Kyl intended to return to lobbying, but, according to The New York Times, he was “eager to return to his lucrative post-congressional life.”

In Kyl’s return to the Senate, he sponsored three bills, including the Estate Tax Rate Reduction Act, which would create a 20-percent tax on estates instead of the current tiered system.

That would actually represent a tax increase on gifts below $10,000, which are currently taxed at 18 percent, while slashing the rate for gifts more than $1 million, which are now taxed at 40 percent.