Speculation is mounting the government could overhaul Australia’s capital gains tax in next month’s federal budget amid reports Treasurer Jim Chalmers is considering scrapping the current 50 per cent discount in favour of the pre-1999 indexation model. Appearing on Sunrise on Monday, Social Services Minister Tanya Plibersek refused to speculate on whether any changes were coming, but One Nation MP Barnaby Joyce warned Australians they were about to get “walloped with a big new tax”.