The Federal Government will release information about the amount of revenue raised by its Mineral Resources Revenue Tax (MRRT) in its regular monthly financial reports, finance minister Penny Wong says.

In last month's mid-year budget review, the federal government downgraded its revenue forecasts for the MRRT to $2 billion, from $3 billion at the May budget, and down to $9.1 billion, from $13.4 billion, over the forward estimates.

The decline was partly a result of a 38 per cent drop in iron ore prices between the May budget and the release of the mid-year economic and fiscal outlook.

Senator Wong was asked during Senate question time on Monday whether she stood by the projections.

"You can't necessarily extrapolate the total annual take by multiplying the first quarter by four," Senator Wong said.

The MRRT was introduced on 1 July, and there are concerns it collected no revenue in its first quarter of operation.

Senator Wong said information about the resource tax collection would be released each month, starting from the October financial report due in December, subject to taxpayer confidentiality rules.