During George Santos’s run for Congress, he told prospective voters that he hoped one day to be able to “serve and give back to our community.”

In his most recent financial disclosures, Mr. Santos, now a first-term Republican congressman representing parts of Queens and Long Island, reported doing just that: He has returned nearly $8,400 in donor contributions.

The refunds exceed the $5,333.26 that Mr. Santos has raised in the first quarter of 2023, a net loss that lowers his cash on hand to just over $25,000, according to the reports filed on Saturday with the Federal Election Commission.

“I don’t think I’ve ever seen a worse report for an incumbent member of Congress,” said Brett Kappel, a leading elections lawyer who advises both Democrats and Republicans.

In contrast, Representative Anthony D’Esposito, a first-term Republican who represents a neighboring district in Nassau County, raised more than $215,000 from individual donors and more than $300,000 from political action committees.

A spokeswoman for Mr. Santos declined to comment on the fund-raising numbers.

Mr. Santos’s filings are the first indication of his campaign’s activity since he filed paperwork last month signaling his intent to continue raising money for a possible re-election bid. Though Mr. Santos has not publicly said whether he plans to run again, the move allows his campaign to keep raising and spending money.

But those hoping that the filings might offer a window into what exactly Mr. Santos has been doing since taking office in January will be largely disappointed. They show no campaign trips or payments to vendors. Nor do they show payments to any lawyers, despite continuing ethics and criminal investigations.

Mr. Santos has sought to blame his campaign finance issues, which prompted the watchdog group the Campaign Legal Center to file a complaint with the F.E.C., on his former campaign treasurer.

Subsequent filings, including the April quarterly filing, have been signed by his new treasurer, identified as Andrew Olson. But with no payments listed in reports, it would seem that he was not compensated by the campaign for whatever work he did for Mr. Santos.

Mr. Santos’s previous treasurer, Nancy Marks, resigned in January, after The New York Times and other news media outlets reported on numerous financial irregularities — from an odd string of payments for $199.99 to hundreds of thousands of dollars in unexplained and unitemized spending.

Of the $5,333.26 in recent donations to Mr. Santos, only one donation, for $254.95, came from a named donor: Sacha Basin, who listed a New York address. The donor could not be reached for comment. Some of the donors who received refunds were similarly not identified; those that were included Mayra Ruiz and Robert Mangi, whose contributions of $2,900 each were returned, and Thomas Zmich, a former House candidate who was refunded $500.

Mr. Zmich explained that the money had been for a bus trip to support Mr. Santos on the day of his inauguration; the trip was later canceled. When asked if he still supported the congressman, he was noncommittal: “I couldn’t say yes and I couldn’t say no.”

Ms. Ruiz, a Republican donor in Miami, gave $10,800 to Mr. Santos’s joint fund-raising committee, and was among the first to give Mr. Santos money after he won the election. She also was one of two wealthy donors who participated in the sale of a $19 million luxury yacht that was brokered by Mr. Santos.

Ms. Ruiz did not immediately respond to a request for comment. Mr. Mangi declined to comment.

Aside from public appearances — a visit to show support for former President Donald J. Trump at his arraignment in Manhattan, several official tours and a handful of television shows and podcasts — it has been hard to account for what Mr. Santos has been up to since taking office.

Ordinarily, House members’ time is taken up by responsibilities related to their committee assignments. But Mr. Santos does not serve on any committees, having opted to resign from his postings at Speaker Kevin McCarthy’s urging. Mr. Santos has introduced four bills, none of which have attracted co-sponsors.

But he has remained a vocal and emphatic presence online, where he has bragged about the value of a Cartier watch, decried the detention of a Wall Street Journal reporter in Russia and declared his loyalty to the New York Mets (albeit somewhat unpersuasively).

And he has spoken 18 times on the floor of the house — the most of any freshman, according to the C-SPAN podcast “The Weekly.” He has used the minute-long opportunities that House members are afforded for a broad spectrum of purposes, from disavowing the possibility of a new nuclear accord with Iran to congratulating Jericho High School on Long Island for being granted exclusive rights to put on a musical based on the Disney movie “Frozen.”