Rail freight operator Aurizon will undertake a share buyback of up to $300 million to reward investors, despite a 13 per cent slide in its statutory net profit, to $473 million.

The Aurizon profit result, from full year revenue of $2.91 billion, easily eclipsed consensus expectations among analysts of an underlying profit of $445 million.

The biggest contributor to the reduced earnings reported by Aurizon was the reduction in charges the group could impose on its customers in fiscal 2019, in response to a decision made by Queensland competition regulators.

Aurizon had been in a long-running legal battle with the Queensland regulator over much it could charge the many companies, including major mining companies, which use its rail network to transport their products. Charges were lowered in 2019 and refunds were given to customers, with Aurizon putting the cost of the move to its earnings before interest and tax (EBIT) at $60 million. The stoush over how much Aurizon could charge is now resolved.