The average cost of care   plans completed in the first three months of the NDIS was almost a third higher than the  average cost during modelling, says the minister responsible for the scheme, Mitch Fifield.

NDIS costs are coming down. Photo: Tamara Voninski TVZ

The National Disability Insurance Scheme is being rolled out under budget, according to a report from the agency implementing the scheme.

The National Disability Insurance Agency (NDIA) says that the average cost of individual packages in the first year of the NDIS was $34,600, compared to the expectation of $35,000.

This follows concerns about cost blowouts earlier in the year, with the average cost of care plans in the first three months coming in at $46,290.

The current average cost figure excludes a large group home in Stockton in the Hunter region, that is "temporarily distorting the numbers". If Stockton was included, the average cost would be $38,200.

In a report released on Monday, the NDIA said that the costs of the scheme were "trending downwards at all trial sites".

The average time it takes to determine eligibility for the NDIS has also dropped from 29.7 days in December to 13.3 days at the end of June.

More than 8500 people have been signed up to the scheme so far, which is about 90 per cent of the target agreed between the federal government and the states.

The report finds that participants are satisfied with the scheme, with a rating of 1.66 (between options of -2 and +2), which is the same as the previous quarter's results in March.

The minister responsible for the NDIS, Mitch Fifield, said the report showed there had been a "herculean" effort with the scheme.

"It is important that the NDIA be a continually learning organisation that can listen to feedback and make adjustments as necessary," he said in a statement.

The latest figures come as the NDIA prepares to submit a report to federal and state governments about whether the timetable for the roll-out needs to be changed.

Some disability advocates are concerned that the federal government is gearing up to delay the implementation of the NDIS.

Trials for the scheme began around Australia in July last year, with the full national roll-out due by 2019.

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