I'm after some advice if anyone can help. My husband and I have a Family Trust which purchased a commercial property from my father's Unit Trust two years ago. My father has since discovered that he has had to pay GST on the sale of this property (he was under the impression that GST did not apply in the sale). Obviously he didn't read the fineprint stating the sale price was GST inclusive. As a result, the effective sale price has been reduced, with my father having to pay 10% of the original listed sale price to the ATO as GST. He is hoping to get this money back, by my Family Trust claiming back the GST and reimbursing him. However, my Family Trust earns under $75,000 and is not registered for GST. Thus, we have never charged GST to our tenants when we invoice them for rent. Should my father kiss this money goodbye, or is there a way we can recoup this money for him i.e. by backdating a GST registration? Our concern with backdating a GST registration is the implication it has on two years of rent invoices we sent our tenants that had nil GST. Any thoughts are appreciated.