Is GST applicable on imported machinery?

Yes. If you pay your GST on a quarterly basis, then import GST is payable at the time of importation, along with any Customs Duty and Customs user fee.

If you are a large importer, then you may have the option of lodging your BAS return monthly and having any import duty deferred and included on your monthly statement. If you think that this may be an option for you, then please discuss this with your accountant.