Feb 8 (Reuters) - Australia's top power and gas retailer Origin Energy ORG.AX said on Thursday it expects to book a post-tax impairment charge of A$533 million ($416.7 million) for its half year results, due next week.
The aggregate charge includes a non-cash writedown of A$360 million for its Ironbark gas field, due to a downgrade in Ironbark reserves and a revised development plan, the company said in a statement.
Origin also expects to book a post-tax impairment charge of A$173 million, as a result of recognising Lattice Energy earnings from July 1 2017 up to the Jan. 31 2018 completion date.
($1 = 1.2791 Australian dollars)