Home Depot, one of the many companies involved in the “options backdating scandal,” has announced that the company has been routinely backdating options for its executives since 1981.

An internal investigation revealed that this practice went on from 1981 until 2000, and it caused Home Depot to understate its compensation expenses by about $200 million. The practice stopped in 2000 when current CEO Bob Nardelli was appointed.

Home Depot is one of the largest companies to admit to backdating, with fiscall 2006 sales of $81.5 billion. The company’s investigation found that the stated grant date of options was regularly earlier than the actual date the grants were approved by the board of directors. The stock price on the approval date was also almost always higher than the price on the date to which the options were backdated.

This discovery will cause Home Deopt to reduce retained earnings by $200 million and increase paid-in-capital by the same amount.