According to financial records reviewed by Insider, Whitehouse has violated a conflict of interest law by failing to report two personal stock purchases.
Whitehouse bought between $15,000 and $50,000 worth of shares in Target Corporation.
The senator disclosed his trades on March 16 after the deadline.
Whitehouse spokesman Rich Davidson told Insider that the filing came two days late.
Whitehouse is a member of the Senate Committee on Environmental and Public Works, which has jurisdiction over air pollution and environmental policy matters. Davidson didn't reply to a question about whether Whitehouse's investment inTesla was a conflict of interest.
Lawmakers who are late with their stock trades face a $200 fine.
Whitehouse won't pay a penalty because the US Senate Select Committee on Ethics allows violators a fine-free grace period, so long as they disclose their stock trades no more than 30 days late. It is not known how often the committee waives even later disclosures, but they do not report this information publicly.
Other members of the US Senate that Insider and other news organizations have found in violation of the Stop Trading on Congressional Knowledge Act include Democrat Dianne Feinstein of California.
Dylan Hedtler-Gaudette, government affairs manager for nonpartisan watchdog group Project on Government Oversight, said that it is critical for lawmakers to comply with these reporting deadlines because it is the law. To put it mildly, this is not a good look.
Whitehouse's late disclosures come at a time when Congress is debating whether to ban federal lawmakers and their immediate family members from trading individual stocks.
Dozens of lawmakers have sponsored or co-sponsored any of the stock-ban bills, and a Committee on House Administration hearing on the matter is imminent.
The Conflicted Congress project in December found that dozens of lawmakers, and at least 182 senior congressional staffers, had failed to comply with the reporting requirements of the STOCK Act.
Conflicts of interest include that four members of Congress or their spouses have invested in Russian companies at a time when Russia has invaded Ukraine.
At least 18 members of Congress, including Whitehouse, have investments in at least one of the two defense contractors that make missiles for the Ukrainian military.
Davidson said that Whitehouse supports a ban and is working with proponents of multiple bills to reach a unified caucus position.
Whitehouse told Politico in 2017: "I don't decide on, neither am I informed of, trades that are made in my account."
Whitehouse has not created a qualified blind trust that requires congressional approval in order for a lawmaker to officially transfer management of their financial assets. Senate guidance says that these trusts provide the most comprehensive approach to avoiding potential conflicts of interest or the appearance of such conflicts.
Members of Congress are personally responsible for publicly revealing their stock trades on time. Members of Congress are trained about federal reporting requirements.
By continually giving the finger to reporting requirements related to their stock transactions, members are telling the public that they don't care about what the public thinks.