Documents filed with Elections Manitoba show Oswald raised $69,726 for her leadership campaign and spent $67,121.
That spending total was just $4,800 under the limit set by party officials.
Oswald came within 33 votes of toppling Selinger at a party convention in March.
Selinger and third-place candidate Steve Ashton have yet to file their financial returns.
Oswald attracted donations from some high-profile Manitobans, including lawyer and philanthropist David Asper and former NDP cabinet ministers Eugene Kostyra and Vic Schroeder.
Oswald was part of a caucus revolt against Selinger last fall, when she and four other senior ministers called on him to consider resigning in the wake of continued low polling numbers.
Selinger rejected the calls to step down and called on the party to hold a leadership race.
While many party members were angry at Oswald and the other rebel ministers, she was backed by many NDP staffers, including many of Selinger's top advisers.
Since losing the battle, Oswald has said she has not yet decided whether she will run for re-election next year.