Once a refundable tax return is lodged, it usually takes the ATO 10 to 14 business days to issue the refund. Your refund will usually be paid straight into your bank account.
As with most things, some hiccups can occur and the time frame could be extended. Some reasons why the refund might be delayed are:
If you have other lodgement obligations which are late.
If you have an outstanding debt on any other ATO account.
If your details entered are incorrect, such as an incorrect bank account.
If the ATO is doing further data checks on your return.
If the ATO is cross-checking your return with the Department of Human Services.
If you lodge through a tax agent, they will usually be able to check the status of your return with the ATO, and when the refund is expected to be paid.