But that certainty will cost the disability support pensions of thousands who could be kicked off the payment.
The federal budget includes $2.1 billion to go into a special NDIS savings fund designed to ensure there's enough money for the scheme when it rolls out for 460,000 people by 2019.
The government claims it helps make up a $4.4 billion shortfall in funding because Labor didn't allocate enough money in government.
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However, the funding will be paid for by reviewing 90,000 people getting disability income support every year on their capacity to work.
Of those, 30,000 people who the government suspects aren't eligible for the pension will have to undergo a medical assessment by a government-contracted doctor.
The fund will also be paid for by abolishing the carbon tax compensation and shelving a planned advertising campaign to promote the scheme.
