The Queensland Treasury included BHP Billiton Group's partner in Australia, Mitsubishi Corp., in a royalty assessment for 2005 to 2015, which could result in tax claims around the miner's offshore trading hub growing beyond A$1.4 billion, The Australian reported May 19.
Mitsubishi's involvement could add over A$300 million in extra royalties in addition to the A$1.1 billion of Australian Taxation Office claims related to BHP's Singapore marketing business.
BHP and Mitsubishi are equal partners in the BHP Billiton Mitsubishi Alliance coal joint venture.
The Australian Taxation Office was already investigating mining heavyweights BHP and Rio Tinto over allegations that the duo lowered their Australian tax bill by funneling billions of iron ore profits through Singapore-based businesses.
The Queensland Office of State Revenue is already chasing A$329 million over a royalty review, which BHP is disputing in the Queensland Supreme Court.
The previous A$288 million claim was increased after a second assessment, covering 2013 to 2015, swelled the royalties to A$225 million with interest of A$104 million.
According to the report, Mitsubishi has now partnered with BHP to contest the royalties, driving the claims against the Singapore marketing hub from both state and federal governments to A$1.8 billion.