bhp the worlds largest miner by market value on thursday said it has been incorrectly deducting leave for some workers for more than a decade and estimated it would cost up to 280 million before tax to remedy the issue the company said a preliminary review has found some current and former employees in its australian operations had leave wrongly deducted on public holidays since 2010 bhp estimated 28500 workers were affected with an average of 6 days of leave incorrectly deducted oz minerals the australian copper miner bhp recently acquired appears to have had a similar issue bhp said there are also about 400 current and former employees at port hedland in northwest australia that bhp has found entitled to additional allowances due to an error in their contract the company said the cost of remedying that is included in bhps upto 280million pretax cost estimate we are working to rectify and remediate these issues with interest as quickly as possible said geraldine slattery the companys australian president