Rio Tinto has ultimately paid no mining tax to the Australian government during the first year of the controversial tax, after pre-payments made in April were refunded by the tax office.

In a blow to the Labor government less than a month before the federal election, review work by Rio and the tax office since June 30 has shown the multinational miner was not liable to pay any tax for the 2013 financial year.

Sam Walsh: Let's get on with life. Credit:Sean Davey

The mining tax forces companies to estimate their exposure and make payments every three months, but the bill is not determined until after the conclusion of each financial year.

The revelation that Rio's pre-payments were refunded has raised the prospect that other companies such as BHP Billiton may have had their pre-payments refunded, too, and comes just a week after the Rudd government downgraded its revenue estimate for the tax over the next four years.