Similar to overpaying tax overseas prior to moving for not completing a whole tax year, it may happen in Australia. From whenever you sign on until the last day of June your tax will be deducted as if equal across payments.
ATO isn’t as scummy/thieving/deceptive or treacherous as others. You will get your overpaid tax back easily and quickly on your 1st return.
Should you wish to use it to cover the unused portion of your Concessional Contributions which rolls forward into new tax years. Talk to your agent before you submit your 1st return, they may suggest you should complete a notice-of-intent-to-claim or a variation.