Apple has offered to re-price stock options for some employees who received them at incorrect prices.

In a filing Friday with the US Securities and Exchange Commission (SEC), Apple said 114,695 options, issued between 1997 and 2002, were erroneously assigned grant dates that preceded the finalization of those grants. As a result, the exercise prices of these stock options were lower than they would have been if the options had been dated when the grants were actually finalized. Because of the error, affected options exercised after 2005 are subject to federal income tax plus a 20 per cent penalty and interest charges. Those who elect to have their options re-priced at a higher level will avoid that tax liability, Apple said.

Employees have until 16 April to ask for the repricing but Apple directors and top executives are not eligible to participate in the offer.

Apple is one of more than 100 US companies conducting stock options internal reviews or being investigated by the SEC for options accounting irregularities, or both. In most cases, stock options were backdated to a date when the price was lower than on the date they were actually granted, giving the holders an instant profit. SEC regulations don't prohibit backdating but there are rules for how backdating must be accounted for and disclosed.

Apple conducted its own internal probe of options backdating in 2006. The probe revealed that 42,077 options had been improperly backdated, including options to CEO Steve Jobs, but that while Jobs was aware of procedural irregularities he did not understand the accounting implications. The investigation revealed that some records were fabricated to state that options were approved at a board meeting that, it turns out, was never held. The company said in December that it was restating its financial results with a total impact of $84 million, including $21 million combined for the years 2004, 2005 and 2006 as a result of the options probe.

However, the SEC and the US Attorney's Office in San Francisco continue to investigate Apple's stock options practices.