Sandra Kuba, who worked at Disney for 18 years, made the claims in whistleblower filings with the Securities and Exchange Commission.
In the filings, Kuba alleged that employees in Disney's parks-and-resorts division recorded nonexistent revenue from free golf rounds and guest promotions.
Kuba told Marketwatch that Disney's revenue could have been overstated by as much as $6 billion — about 20% — in 2009 alone.
Disney told government investigators it fired Kuba because "she displayed a pattern of workplace complaints against coworkers without a reasonable basis for doing so, in a manner that was inappropriate, disruptive, and in bad faith," according to Marketwatch.
In June, she alleged that some Disney employees tried to slash the firm's sales tax liabilities by reclassifying revenue from highly taxed items such as hotel rooms as revenue from lower-taxed items such as food and beverages, Marketwatch reported.