While some had positive comments about the life-changing scheme, the bulk of the evidence before the joint parliamentary committee was negative with complaints of lengthy waits for assessment by planners with little knowledge of complex disabilities.

At times emotional families told the committee they feared their loved ones would be left worse off as the NDIS takes over disability service provision.

Several participants and providers spoke of the "gobbledygook" used by National Disability Insurance Agency planners making it difficult to understand the criteria to gain support.

ACT Disability, Aged and Carer Advocacy Service chief executive officer Fiona May said the organisation received many calls from participants overwhelmed and confused by the volume of information and jargon.

"We have raised with the agency [NDIA] that we're concerned the plans are incomprehensible to people," she said.

"The templates and processes are not easy to understand and the new language ... creates a significant barrier for people to argue their case successfully."

Ms May said she knew of one family whose access was arranged exactly within the 21-day period and another still waiting after five weeks.

NDIA general manager Liz Cairns said 12 of the agency's "most accessed" documents had been translated into easy English on its website as of Friday, but admitted the planning documentation was yet to be revised.

Committee member Jenny Macklin said it was a serious problem that had to be addressed.

Ms Cairns said work was ongoing to simplify the plans and provide more flexibility for participants to choose where their money was spent.

Autism Aspergers Advocacy Australia convener Bob Buckley was one of several people who raised concerns about the "variable" knowledge of planners.

Ms Cairns said there was a "robust" quality assurance framework, but admitted planners had "varying degrees of expertise".

Ms Macklin said planners appeared to be under "enormous pressure" with data suggesting they were failing to meet targets.

She questioned whether there were too few in the ACT.

But the NDIA's ACT manager Jillian Paull said the ACT was one of only two sites to meet its second-quarter target.

The NDIA's Alice Tibbets said the agency was advertising for more staff to cope.

The committee also heard of discrepancies in the amount of funding for participants with similar needs.

Just Better Care owner Fergus Nelson was one provider to cite examples where participants had "undoubtedly" received more than they needed while others were left deflated after coming away with little or no funding.

Committee member Senator Zed Seselja agreed and said a provider had told him the amount of funding appeared to hinge on the participant's ability to explain their needs.

But Ms Paull defended the packages saying the agency was "pleased" each plan was unique.

"It isn't useful to say there are two children in the world who have similar needs and have different looking packages for different amounts of money because that's a gross oversimplification of the process," she said.

Several participants and providers complained of a reduction in respite hours for carers.

Ms Tibbets said the agency had heard the concerns and were in discussions with the pricing team about introducing an evening, overnight and weekend respite rate for children.

Others criticised a policy to strip 20 minutes from each hour of care to cover transport provision.

"Everyone loses out, the client gets 20 minutes less, the worker gets paid 20 minutes less and the providers are bearing the brunt of it," DUO Services chief executive Cheryl Pollard said.

Ms Cairns said the concerns would be addressed in ongoing pricing work, but said it came from advice from independent experts.

Several carers said planners had limited the amount of transport funding available in each plan.

Ms Cairns said there was no cap, but the guidelines were "frequently misunderstood".