In a letter to the Federal Election Commission posted Wednesday on the agency's website, attorney Cleta Mitchell writes that the Delaware Republican's campaign could not afford compliance professionals to oversee its spending until late in the campaign.
Mitchell says the campaign is working to reconcile all bank entries with federal spending reports.
O'Donnell has faced scrutiny over her campaign practices, including allegations that she used political donations for personal expenses such as rent. The Associated Press reported last week that federal authorities were investigating her spending.
