The tax, which has the votes to pass Parliament even before it is unveiled tomorrow, will rise each year by a predetermined amount (perhaps 3 or 4 per cent plus inflation).

The all-important emissions reduction target for the trading scheme will be set with the help of advice from an independent expert committee.

The trading scheme will have an upper ''price cap'' and lower ''price floor'' to guard against wild price fluctuations.

It will include some limit on the extent to which the 500 companies who have to buy pollution permits can buy them on overseas carbon markets.

The Greens voted against the Rudd government's emissions trading scheme because they thought it locked in too low a target. Continued disagreement on this point is the whole reason this scheme is starting with a fixed price.

The scheme will not cover agriculture or fuel, but the government will reap extra revenue by charging miners and some other industries a nominal carbon price on their diesel fuel by cutting their excise rebate.

The initial price impact of the tax will be less than 1 per cent, which previous Treasury modelling suggests would translate into an impost of less than $10 a week for the average family. Nine out of 10 families will receive either tax cuts or increased family or pension payments or both to at least partially compensate for the higher prices.

Almost seven out of 10 families will be fully compensated, with low-income families and pensioners about 20 per cent better off and pensioners getting extra payments upfront.

Trade-exposed industries will get much the same assistance as they were promised last time, with ''gassy'' (high-methane) coalmines getting a little less ($1.275 billion this time). Steel and other manufacturers struggling with the high dollar have won additional assistance in grants to help fund technology to reduce their emissions.

Electricity generators are likely to get another $7.3 billion in compensation and the most emissions-intensive will be able to tender for subsidies to close earlier than planned.

There will be a $2 billion Clean Energy Financing Corporation, independently administered, which will provide loans, loan guarantees or subsidies to large-scale solar or gas investments, and a separate renewable energy agency to combine and independently administer $3.2 billion scattered across a grab bag of different programs.

The whole package was supposed to be revenue neutral, but is likely to cost about $4 billion more than it raises from selling pollution permits in the first four years. Much of this will be recouped through measures such as cutting the diesel rebate.