In v3, the transaction-level gst has the same sign as amount. Money leaving the business (a card purchase, a charge) has a negative amount and a negative gst. Money coming back (a refund) has a positive amount and a positive gst. This matches the Weel transaction report export, so you can sum gst across transactions to get the net GST without looking at the transaction direction.
| Transaction | amount | gst (v2) | gst (v3) |
|---|---|---|---|
| Purchase | -9.99 | 0.91 | -0.91 |
| Refund | 9.99 | 0.91 | 0.91 |
A gst of 0 or null is returned as is.