I want to reverse an invoice payment, how do I do this?

Hi there, bstavik.

QuickBooks is partnering with PayPal to receive customer's payment online in QuickBooks Online for Australia. I'd suggest reaching our to PayPal's support to inquire if there's a way to reverse your customer's payment.

If you're just recording the payments manually in QuickBooks, you can find the payment transaction under your customer's Transaction list. Then, you can open and delete it.

You can always go back to this thread if you have other questions.