Westpac Banking Corp., one of Australia's largest banks, has posted a 15 percent fall in its annual profit to 5.97 billion Australian dollars ($6.17 billion) due to the tax implications of its takeover of smaller rival St. George Bank.

The result for the year through September announced on Monday was down from AU$6.99 billion for the same period the previous year, when Westpac received AU$1.1 billion in tax benefits.

Australia's four largest banks have reported mixed results. National Australia Bank last week posted a 22 percent fall in its annual profit to AU$4.08 billion due to bad debts and restructuring costs of its troubled British operations.

Commonwealth Bank of Australia Ltd., up 11 percent to AU$7.1 billion, and ANZ Banking Group Ltd., up 6 percent to AU$5.7 billion, posted their best ever results.