WinRed charges a standard fee (as of last year, 3.94 percent) on every donation, which is paid by the campaign or committee that receives the money. But Mr. Santos seemed to suggest a different arrangement that was reported earlier by NBC News.
Mr. Santos, who received $796,238.26 from WinRed, according to that company’s F.E.C. filings, should have paid roughly $33,000 in fees. Instead, his filings to regulators show payments adding up to more than $206,000 — an appropriate fee only if Mr. Santos had taken in roughly $5 million.
The overpayment leaves roughly $173,000 in fees unaccounted for.
In a statement, WinRed said it “proactively reached out to the campaign to ensure its agency fees were being reported accurately.”
Paul S. Ryan, an expert in campaign finance law, suggested that Mr. Santos may be “inflating the payments to WinRed and pocketing them for personal use,” something that he said the F.E.C. might not notice because WinRed expenses are so common among candidates.
“The best way to avoid scrutiny is to file reports that appear plausible on their face,” he added.
The accounting problems extend to Mr. Santos’s reported generosity to other candidates, records show. During the campaign, his primary campaign committee and leadership PAC gave more than $180,000 to other campaigns and committees. But the amounts and names listed on his filings did not always match what his recipients recorded, The Times’s analysis found.
Mr. Santos’s leadership fund, GADS PAC, reported sending two donations of $2,900 each in July of last year to Michelle Bond, a Long Island Republican who lost a primary challenge to Representative Nick LaLota. But Ms. Bond’s records show a single donation of $5,000 from the PAC in August, $800 less than what Mr. Santos had reported.
Mr. Santos also sent two separate $2,900 contributions from his leadership PAC to Blake Masters’s unsuccessful Senate bid in Arizona, according to filings from Mr. Santos and Mr. Masters.