Rep. Markwayne Mullin (R-Okla.) stands with his family as he gives his victory speech in 2012 in Muskogee, Okla. (Michael Wyke/Tulsa World/AP)

The House Ethics Committee on Friday announced that it would not place financial sanctions on Rep. Markwayne Mullin after a nearly five-year investigation into his business dealings, though Mullin has been ordered to return $40,000 he had received from a family company.

Mullin (R-Okla.) faced allegations that he broke House rules by appearing in commercials for his family plumbing business and received improper payments for his role as a president and director of various family companies.

But the report credited Mullin with seeking the panel’s guidance on how to handle his business dealings shortly after his 2012 election and, with respect to the $40,000 payment, found that “an accounting error led Representative Mullin to inadvertently fail to fully follow” the panel’s guidance.

In short, while Mullin did transfer ownership of one of his companies that held a federal contract pursuant to Ethics Committee guidance, the company disbursed profits to him as though he were still an owner.

“Ultimately, the Committee determined that Representative Mullin made a good-faith effort to seek the Committee’s informal guidance on numerous issues with respect to his family business,” the report said. “To the extent that Representative Mullin substantially complied with the Committee’s advice, it would be inequitable to subject his conduct to additional review.”

The independent Office of Congressional Ethics first referred allegations to the committee in December 2013 for further investigation and potential sanctions.

The Ethics Committee report comes at a moment when Mullin is under scrutiny for another business matter: He is among a handful of House Republicans who invested in Innate Immunotherapeutics, an Australian pharmaceutical start-up whose largest shareholder is Rep. Chris Collins (R-N.Y.).

Innate’s sole product, a drug meant to treat multiple sclerosis, failed a high-stakes clinical trial last year, leaving its stock nearly worthless. Collins was charged Wednesday with insider trading, helping his son and other relatives unload shares before the results of the trial were made public, saving them hundreds of thousands of dollars in potential losses.

Friday’s report makes no mention of Mullin’s investment in Innate, which was valued in a financial disclosure statement at between $100,000 and $250,000 at the time of purchase in January 2017. A spokeswoman, Amy Lawrence, said Wednesday that Mullin still owns his Innate stock, and he has not been accused of wrongdoing with regard to the investment. Collins on Wednesday called the charges against him “meritless.”

As for Mullin’s dealings with his family business, the panel found it “raised several novel questions regarding the application of House rules and other standards of conduct to a Member’s efforts to maintain and promote a family business.”

Mullin appeared in commercials promoting his family companies and hosted a weekly radio show on home improvement issues also meant to drum up business for his firms. At the time, the Ethics Committee advised him that he could continue airing the old ads and hosting the radio show as long as he was not paid for it.

The new guidance is clear: “Under no circumstances should a Member be actively involved in personally selling or endorsing goods or services in which the Member has a financial interest,” the report says — regardless of whether there is direct compensation.

Mullin said in a statement Friday that the new guidance would only make it hard to be a “citizen legislator.”

“You have to be a career politician to serve in Washington, D.C.,” he said. “If I don’t fit the bill for a citizen legislator as a plumber, rancher, and someone who had never held a political office before, then who does?”

The committee also set aside questions about whether Mullin received improper compensation for serving as a director or officer of his companies. According to the report, Mullin gave conflicting answers about what precisely his role was, but the panel concluded “his actual responsibilities in the day-to-day operation of the companies were significantly reduced” upon his election to the House.