The Road Transport Association (RTA) in South Australia says the trucking industry is being overcharged millions of dollars in tax every year.

The group wants the overcharging issue to be addressed at a meeting of state and territory transport ministers with the federal Infrastructure Minister in Adelaide next week.

RTA executive director Steve Shearer says National Transport Commission (NTC) figures show federal and state governments collect about $250 million more tax than was spent on the nation's roads.

Mr Shearer says there is an error in calculations because of an outdated formula.

“If you take someone who runs a B-double, they're being overcharged by 17 per cent — over $2,000 per year, per truck,” he told reporters this week.

“It just doesn't make sense on any level, other than government failure to do the right thing and live within their means.

“[The NTC] told them [about the calculation error] 18 months ago and all the transport ministers did nothing about it.”

Freight company owner Sharon Middleton says her business must maintain 150 registrations each year, and she believes it is unjust for governments to collect so much more than they need.

“To consider that we're being overtaxed $250 million in this business is unacceptable, considering all the other taxes we're paying,” she told the ABC.

“We're taxed on everything we do.”

South Australia’s Transport Minister Stephen Mullighan claims the Government is trying to keep costs down for the trucking industry.

“Last year South Australia fought against proposed increases of up to 38 per cent for some heavy vehicles,” he said.

“As a result we saw the smallest increase in heavy vehicle registration fees in three years.

“We are wary of how a significant increase in heavy vehicle registration charges could flow on to consumers so we will need to carefully consider any proposal to raise heavy vehicle registration charges.”