Rio Tinto PLC (LON:RIO) said it will dispute extra taxes demanded by the Australian Taxation Office.
The miner received amended assessments of A$359.4mln (£200mln) primary tax and A$47.1mln (£26mln) of interest, relating to the denial of interest deductions on an isolated borrowing used to pay an intragroup dividend in 2015.
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This is in addition to the A$8.4bn (£4.6bn) of Australian income tax paid during the relevant period.
The FTSE 100 group said this borrowing was repaid in 2018 and borrowing to fund the payment of a dividend is “a normal commercial practice”.
It added that it is confident of its position and will dispute the assessments, while it will pay 50% of the primary tax up-front as part of the objections process “in accordance with the usual practice”.
Shares were flat at 6,301p on Tuesday morning.