Representative Alexandria Ocasio-Cortez made a splash when she arrived at the 2021 Met Gala in a designer dress with “Tax the Rich” emblazoned across the back. Four years later, she is still settling the bill.

Ms. Ocasio-Cortez, a New York Democrat and leader of her party’s progressive wing, personally paid about $1,000 to rent the dress and accessories. But in a report released on Friday, the bipartisan House Ethics Committee concluded her initial payment had fallen short of the fair market rate, violating House rules.

While the committee found no reason to believe that Ms. Ocasio-Cortez was trying to stiff the vendors, it wrote that “it would be appropriate” for her to pay an additional $2,733.28 to cover what it determined was the full value of her outfit.

The panel also urged the congresswoman to make a $250 donation to the Met’s Costume Institute, the beneficiary of the star-studded annual gala, to cover the cost of a meal for her partner, Riley Roberts, who accompanied her. Once she did, the panel would close the yearslong investigation, it said.

“While the committee did not find that Representative Ocasio-Cortez’s violations were knowing and willful, she nonetheless received impermissible gifts and must bear responsibility for the other conduct that occurred with respect to the delays in payment,” the 31-page report said.

Mike Casca, the congresswoman’s chief of staff, stressed that the committee noted she had tried to comply with House rules. Still, he said she would personally take responsibility for the outstanding balance.