While calculating the tax damage varies from company to company, a recent Queensland Resources Council survey found the average effective tax rate expected by the surveyed companies was 58% under the resources super-profits tax.

This includes the corporate tax rate set under the May budget which unveiled the recently replaced RSPT policy.

One of the changes to calculating effective tax is that under the MRRT the federal government is required to abandon the budget measure to drop corporate tax rates 1% to 28% in 2013.

The new tax policy not only cuts the tax rate from 40% to 30%, and puts the taxable threshold for resource extraction profits north of 12%, but also allows a 25% “extraction allowance” which is yet to be explained in detail.

BDO tax manager Larras Moore told ILN he expected most coal mining companies to be facing effective tax rates at the mid-40% range under the MRRT.

But he said mining companies facing a lot of financing costs could possibly end up with a higher effective tax rate.

He is also keen for the government to provide more detail on the extraction allowance.

The move to allow miners to use market value assumptions rather than book value ones for treatment under the MRRT will also mean coal companies will have to perform further evaluation.

“If you got projects with old assets going through the market evaluation approach versus the cost approach you are going to have to go through it,” Moore said.

“It is going to be a numbers game.”

While noting it might be intuitive to some companies, he said the bulk would have to crunch the numbers to see whether they were in a better or worse position under the two approaches.

Moore previously held corporate tax roles with Xstrata Coal and Rio Tinto.