The obligation on companies under the continuous disclosure rules mean “there will be a trigger to disclose to the market when there is a material development”

“For some companies, the trigger may well be squeezed on Sunday,” ASX spokesman Matthew Gibbs told the Australian Financial Review.

Reports have emerged today of a $A23 a tonne carbon price, after Australian Prime Minister Julia Gillard confirmed the price would be lower than that demanded by The Greens, but in line with that sought by independents Tony Windsor and Rob Oakeshott.

Previous modelling pointed to a $23/t price, excluding petrol, which would push overall costs through the economy by 1%, electricity prices by between 10% and 15% and food by 1%.

The government has also forecast that 500 businesses will have a carbon tax liability.

The Greens have been pushing for a $30/t price.

Any income tax benefits will not be indexed for inflation, but any tax cuts to compensate households will be adjusted to keep pace with higher carbon costs.