He also said that the Pentagon inspector general has informed the Oversight and Government reform panel that Flynn is now being investigated over the payments from Russian Federation and whether or not there was appropriate reporting and approval.
In comments to the AP, Chaffetz said that Flynn "had an obligation to seek approval to take money from a foreign government". In failing to disclose the payment, Flynn may have violated the Emoluments Clause of the US Constitution, which prohibits retired military personnel from receiving payments from foreign sources without advance permission.
Flynn is also the subject of congressional probes into Russian interference in the 2016 presidential election that U.S. intelligence agencies have said was meant to sway the vote in favour of Trump over Hillary Clinton.
In December of 2015, Flynn was paid $45,000 to speak at an event hosted in Moscow by the Kremlin-backed network RT, during which he was seated with Russian President Vladimir Putin.
Flynn has previously disclosed that he received between $50,000 and $100,000 as part of his personal stake in $530,000 that his company, Flynn Intel Group, received for consulting work performed past year for a Turkish businessman. "He was supposed to seek permission and receive permission from both the secretary of state and the secretary of the Army prior to traveling to Russian Federation to not only accept that payment, but to engage in that activity". Any debt collection due to an emoluments clause violation is capped at no more than what an individual makes in retirement pay during a period of unauthorised employment.
Flynn, who was President Trump's first national security adviser, was sacked after it was discovered that he misled Vice President Mike Pence about conversations he had with a Russian official.
The latest release of documents comes amid congressional investigations of possible ties between US President Donald Trump's election campaign and Russian Federation.
Today, Cummings cited an October 8, 2014, letter to Flynn from the general counsel of the Defense Intelligence Agency that the ranking member described as "explicitly warning Flynn, as he entered retirement, that he was prohibited by the Constitution from receiving payments from foreign sources without advance permission". "And we have no evidence - zilch - that he obtained permission from the secretary of the Army and secretary of State to accept any foreign government payments as required by law", said Cummings.
Though the disgraced former national security advisor hasn't been charged with a crime yet, Flynn's lawyer, Robert Kelner, issued a statement March 30 offering testimony in exchange for an immunity deal.
Another Defense Intelligence Agency released Thursday also revealed they could not locate any records of Flynn "seeking permission or approval for the receipt of money from a foreign source".
Mr Flynn's company received three payments between September and November from Inovo BV before Mr Trump was elected president and the arrangement was discontinued, according to Mr Flynn's filings. Flynn is the majority owner and chief executive officer of the firm.
The committee's ranking Democratic member, Elijah Cummings, also released a 2014 document given to Mr Flynn by his old employer, the Defense Intelligence Agency (DIA), which outlines his ethics restrictions - including a prohibition on accepting payments from foreign governments.
"These documents raise grave questions about why General Flynn concealed the payments he received from foreign sources after he was warned explicitly by the Pentagon", Cummings said in a statement.
Such payments possibly violate Defense Department and United States constitutional prohibitions on retired military personnel conducting activities involving foreign governments without advance clearance. The watchdog's office did not discuss the investigation publicly until after the House Oversight Committee released documents about it, and typically does not disclose what it is reviewing while an investigation is underway.