Negotiations between the territory and Commonwealth over which government would provide more funding to participants beyond the initial target of 5075 stalled during caretaker mode prior to the ACT election.

Though both tiers of government have agreed the scheme is uncapped, disputes remain over agreements on funding for any participants above "targets" set for the ACT.

The 2016-17 target was reached in September, with federal Social Services Minister Christian Porter saying funding for any new participants would need to be negotiated following the appointment of a new territory minister after the October 15 election.

The NDIA sent advice to disability services groups last month that "further agreement between governments is required on the full-scheme funding arrangements", with new participants only to be approved as others "exit the scheme".

But new ACT Disability Minister Rachel Stephen-Smith has reiterated the stance of Community Services Directorate Michael De'Athe, who said during the caretaker period that a bilateral agreement in 2012 guaranteed Commonwealth funding for participants beyond the target figure.

"The 2012 agreement went right through to 2019," Ms Stephen-Smith said.

"The federal government made it clear that this was not a capped scheme since then."

Discussions have resumed between the directorate and the federal government about planning meetings about the NDIS rollout in the ACT.

Ms Stephen-Smith said the directorate contacted the National Disability Insurance Agency upon becoming aware no further meetings had been planned in September.

"Those meetings have resumed and we're working to get more participants into the scheme," she said.

"We remain in discussions with the Department of Social Services. It's a big job, but we have to be able to keep things consistent with the agreement."

The 2012 agreement allowed everyone eligible for the NDIS to join from July 1, 2016 after an age-based transitional period from 2014.

It also allows for "portability of arrangements between participating jurisdictions" and notes there may be a "change in the phasing methodology" if participant numbers are significantly higher than estimated.

The total cost for NDIS-funded supports in the 2016-2017 financial year was estimated to be $201.5 million in the 2012 agreement, based on the enrolment of 5075 participants.

Speaking Out For Autism Spectrum Disorder chairman Bob Buckley said the disability sector deserved explanations for why the intake had stopped during the election period.

"We recognise that getting the NDIS up and running in a short time-frame is a challenge; we acknowledge that the NDIA is having considerable success," he said in a letter.

"However, for many it is falling well short of its promises and potential."