On the 3rd of February 2009 the Prime Minister and The Minister for Small Business announced; this was updated in the Budget on 12 May 2009:

The Government will fund an investment allowance / tax break for all Australian businesses.

Small businesses (those with turnover of $2m or less a year) can claim an additional 50% tax deduction for eligible assets costing $1,000 or more that they acquire from 13 December 2008 to 31 December 2009, and install by the end of December 2010.

For all other (read BIG) businesses:

They can claim a 30% tax deduction for eligible assets costing $10,000 or more if acquired between 13 December 2008 to 30 June 2009, and install by the end of June 2010.

Also for eligible assets costing $10,000 or more that they acquire from 1 July 2009 to 31 December 2009 they can claim an additional 10% deduction where they are installed by 31 December 2010.

Eligible assets for the allowance are NEW tangible assets and  NEW expenditure on existing assets used in carrying on a business for which a deduction is available under the core provision of Division 40 (Capital Allowances) in the ITAA1997.