Tuesday's budget predicts the carbon price in 2015/16 will be just $12.10.
Last year, the government expected that price to be $29.
Because of the price revision, the carbon tax is now predicted to bring in $20.7 billion over the next four years, with receipts falling once the floating price comes in.
The tax take is about $3.7 billion lower than estimated in the mid-year budget review last October.
Tax cuts planned to start in July 2015 will be deferred until the carbon price hits $25.40.
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This is expected to save the government $1.5 billion over the forward estimates, although they are likely to be put off for longer than that since the carbon price isn't likely to recover
until 2018/19.
The government says holding off these planned tax cuts won't hurt anyone because the lower carbon price means cutting emissions costs less, so not as much assistance is needed.
The drop in revenue also means funding has been reduced for some clean energy programs.
Coal industry assistance will be cut by $274 million while $662 million of uncommitted funds for low-emissions coal and carbon capture and storage flagships will be returned to the budget.
Almost $160 million of unallocated solar flagships funding will be returned to the Education Investment Fund.
Funding for the clean technology programs, the biodiversity fund and the Australian Renewable Energy Agency will be adjusted to be spread out over an extra two years.
HOW MUCH WILL LABOR'S CARBON PRICE REGIME RAISE:
Budget projections:
* $4.2 billion in 2012/13
* $6.3 billion in 2013/14
* $6.4 billion in 2014/15
* $4.6 billion in 2015/16 (move to floating price)
* $3.4 billion in 2016/17
Other forecasts:
* Carbon price now estimated at $12.10 per tonne in 2015/16,
down from $29
* Price then forecast to rise to $25.40 in 2018/19
