Conservative Leader Erin O'Toole spent $3.69 million on his campaign to win leadership of the party last year.
But having raised over $3.7 million, he ended the race with a small surplus.
All leadership candidates for political parties must submit detailed financial returns due six months after the race ends.
The Conservatives marked that milestone this week, but two of the final four candidates have asked for an extension.
Elections Canada says Peter MacKay asked for an extra 90 days and Derek Sloan asked for another 120 days.
Leslyn Lewis, who finished third in the race, spent $2.2 million, and also finished with a small surplus.