Over the next two weeks it will hear evidence from survivors who have sought redress for abuse suffered in state care and from others who have dealt with government agencies on behalf of claimants.
The state redress public hearings were to have been held in April but were delayed because of the Covid-19 lockdown.
The commission's lead counsel for the hearings, Hanne Janes, said witnesses will share their own experiences.
"So the survivors will explain the institutions that they have been in, their experiences that they have gone through and then the process of redress and how that worked for them."
Twelve survivors will give evidence over the next two weeks, and two organisations will appear, plus two lawyers representing a number of claimants.
Janes said public hearings are only a small part of the commission's work.
Commissioners have held private sessions with 532 survivors over the past few months.
"So there is a lot of information from claimants that we are able to draw on and aggregate that information as to what are their views and experiences of redress and also what other aspects of abuse in care were.
"Evidence being heard at the public hearing is very much representative of a lot of other information we have heard from survivors," she said.
Lack of 'transparency, independence' - lawyer
The firm, Cooper Legal, represents more than 1400 claimants.
Its principal, Sonja Cooper, describes the redress phase of the commission's work as probably its most important.
''We've been saying for a very long time that there are insurmountable problems with the state processes, the lack of transparency, the lack of accountability and I think our biggest issue is the lack of independence. We are very clear and will be giving strong evidence to the effect that the state processes are broken."
She said there cannot be a system where an abuser, and that is the state, investigates itself.
"It just can't be done in a way that is fair to survivors."
Cooper said the public and the state need to hear the evidence and understand what it has been like for survivors.
"How it has impacted on them, how legal aid funding issues have impacted on them."
She eventually wants one independent body set up to deal with abuse, not the complex route survivors have to negotiate now.
"You know, if they were abused in the care of the state through Social Welfare, or CYFs [Child, Youth and Family], you know that is one claim. If they were in a Ministry of Education special residential school, that's a separate claim. A health camp, that is another separate claim or in church care, more claims. So one client may have to deal with five to six different entities which means you are not dealing with the person as a whole, you are compartmentalising their experiences."
She said it is then easy to cherry-pick what is going to be or not going to be accepted and minimise those experiences.
"Obviously that affects whatever compensation they are ultimately offered as well."
Cooper said setting up the independent body would take time but New Zealand has examples of how it could be set up.
"We've got the Waitangi Tribunal and tribunals that hear other claims."
In the meantime though, she wants the commission to put out an interim report within six months of the redress hearings finishing, recommending among other things the repeal of the limitation period of bringing claims for abuse and the proof that is required.
The commission has until 2023 to report back, but Cooper is in no doubt the time will need to be extended.
"Its terms of reference are the broadest of any royal commission of this kind ever.
"For it to do its job properly that deadline would have to be pushed out in fairness to it, because it's been given a massive task to do."
The first part of the redress hearing with survivors will be followed later in October with two weeks of Crown witnesses describing processes available around redress and responding to the survivors' evidence
Faith-based care will come under the spotlight at a later date.
Where to get help:
• 0800 543 354 (0800 LIFELINE) or free text 4357 (HELP) (available 24/7)
• https://www.lifeline.org.nz/services/suicide-crisis-helpline
• YOUTHLINE: 0800 376 633
• NEED TO TALK? Free call or text 1737 (available 24/7)
• KIDSLINE: 0800 543 754 (available 24/7)
• WHATSUP: 0800 942 8787 (1pm to 11pm)
• DEPRESSION HELPLINE: 0800 111 757 or TEXT 4202
• NATIONAL ANXIETY 24 HR HELPLINE: 0800 269 4389