Eligible National Disability Insurance Scheme (NDIS) clients are waiting up to a year for coverage plans despite being approved for funding, a South Australian MLC has said.

Dignity for Disability MLC Kelly Vincent said people were being accepted into the scheme but were then being told they would need to wait before a coverage plan could be drawn up.

"Our office is certainly aware of people waiting up to a year, from the time they've been told 'yes you're eligible to meet the criteria' to putting together plans which lead to a funding package," she said.

"I would say there are hundreds of people in that category."

The State Government said there were about 7,800 South Australians between the ages of zero and 14 receiving services via the NDIS.

From January 1 next year the second phase of the staggered roll-out will extend eligibility to those aged 15 to 17, adding about 2,000 more people to the scheme.

Ms Vincent said the NDIS has been plagued with "teething issues", including computer glitches that have been blocking payments to some NDIS service providers since July.

She said there had been some improvements but it was crucial all the issues were ironed out as soon as possible.

"Certainly things are still not perfect, but I wouldn't say we have the same halting or bottlenecking of the scheme that we saw just a couple of months ago," Ms Vincent said

"Full fixes are expected around late December so I am hopeful we'll be ready. In fact, we have to be ready. There is no option."

SA Minister for Disability Leesa Vlahos advised families to start the process now.

"For families out there at the moment, we'd like you to engage with the NDIS, start planning and then your program and plan can be approved in January when we start, " she said.

"It's important that families start planning for their goals and their children and their young adults to be able to live rewarding lives that the NDIS will provide."

Accessing NDIS would be 'life-changing'

Callum Watkins, 16, has autism and an intellectual disability.

His mother Naomi said accessing the NDIS would be life-changing.

"This will be the first time we'll be getting some really significant support," she said.

"Especially because of his age and moving into adulthood as well this will hopefully create that extended community network for him.

"He's going to be valued as his own individual as well instead of being just a child with disability and having a future like other young people should have at his age."

In a statement, the National Disability Insurance Agency (NDIA) said it expected to bring children aged zero to 14 years, who are receiving existing State Government services, into the NDIS by December 2016.

It said those who were not receiving state funding were scheduled to enter the scheme before June 2017.