The ATO has updated its website guidance on applying GST to ‘face value vouchers’ and ‘non-face value vouchers’.
A face value voucher is one that can be redeemed for a reasonable choice of goods and services. For face value vouchers, you only account for GST when the voucher is redeemed for taxable goods and services, not at the time that the voucher is sold. This is because the sale of a face value voucher for an amount not exceeding its face value is not a taxable supply.
If the face value voucher expires or is not fully redeemed, then an increasing adjustment will generally need to be made on 1/11th of the unredeemed balance.
If you buy a face value voucher and use it to acquire something for business purposes that is subject to GST, then you would normally claim GST credits when the voucher is redeemed, not when the voucher is purchased.
A non-face value voucher can only be redeemed for specific goods and services. GST applies at the time the non-face value voucher is sold, but only if it is redeemable for taxable supplies. When purchasing a non-face value voucher, you claim GST credits in your BAS for the reporting period when the voucher is bought.