If you have made a capital loss, or have made a capital gain and do not choose scrip for scrip rollover, use your calculation of your capital gains and/or losses when completing Item 18 (capital gains) in your 2008-09 tax return (supplementary section).
If you have made a capital gain and held your St George shares for at least 12 months, you may also be entitled to the CGT discount of 50%.
The cost base of your new Westpac shares is $17.1882 multiplied by the number of shares received. For capital gains tax purposes, you acquired these shares on 1 December 2008.