Under federal law, this spring's deadline was May 17. But candidates are given a 30-day grace period to submit the report detailing their personal financial status.
That deadline was up Wednesday. The Senate's Office of Public Records said late Thursday, it had not received a filing from Paul since last October.
Paul campaign manager Jesse Benton says the campaign has filed a request for a 14-day extension.
Paul, a Kentucky eye doctor and tea party favorite, will face Democrat Jack Conway in the fall.
Conway has an extension to file his financial report.