Time of supply: when GST becomes payable

Time of supply is the point at which a supply is treated as made, so GST becomes payable and it falls into that month's or quarter's return.

Goods and services

For most supplies it is the earlier of the invoice date (or the last date by which the invoice should have been issued) and the date of payment. Issuing your invoice on time is what keeps time of supply clean.

Advances

For services, GST on an advance is generally due when you receive the advance. For goods, GST is due on the invoice. See handling advances.