The only person who would ask is the airline. If flying Jetstar you will most likely uses a self check-in kiosk so nobody will ask. It is not a compulsory information to fill for the TDAC just leave it blank
yes i went to do my first 12 month extension and put my passbook into the machine to get updated also received the letter from the bank about 800k. I did not check my book. Went to immigration then worked out oops it just updated the balance to the current month and any transactions that month. Had to go back to the bank and got a statement printed out for 60+ days i had the account.