People with down syndrome, cerebral palsy, Huntington's disease and foetal alcohol spectrum disorder will now have early access to money they have in KiwiSaver.
The government has confirmed the list of life-shortening congenital conditions that will allow people to withdraw their savings early.
People with these conditions will be automatically entitled to apply to withdraw from their fund at a time that is right for them to retire, rather than once they turn 65.
"The conditions on the list were approved because they are known to shorten a person's life expectancy below 65 years," Commerce and Consumer Affairs Minister David Clark said in a statement.
Others born with life-shortening congenital conditions, which may be might be rarer conditions, are still available under the new provisions.
The only additional requirement is for a medical practitioner to verify that the person suffers from a life-shortening congenital condition.
"The previous requirement for people to be 65 to access their retirement savings puts those born with life-shortening conditions at a significant disadvantage," the minister said.
The list of conditions was developed in consultation with health and disability experts, and there is flexibility for the government to review the list periodically to ensure it is up-to-date, he said.
"Tim Fairhall and his mother Joan have been fearless advocates for this work, which led to the law change in 2019. The announcement today is a further testament to Tim and Joan's work.
"It's only right that the KiwiSaver scheme is fairer for everyone, and the government has made changes to ensure that happens," Clark said.
IHC director of advocacy Trish Grant told Midday Report people with other conditions could also apply with their doctors' support.
"It's a great advocacy triumph ... it not only creates an entitlement for flexibility for certain groups, but there's also a pathway for other people too to get that more flexible response to have access to their KiwiSaver fund prior to 65."
She said Tim Fairhall played a huge role in getting the change across the line.
"It's all credit to him and his mother Joan that they held the faith and kept talking to people in government until they listened and responded.
"We heard today from the chief executive of the New Zealand Medical Association, welcoming this news and promoting GPs as the right people to do that sign off."
The regulations under the KiwiSaver Act 2006 come into effect on 26 March.