The income earned during that time of nearly $400,000 was paid to Waipuna Hospice on an annual basis.
The 15 years has now expired and a final distribution of the trust assets of more than $600,000 has been donated in full to the hospice.
Chief executive Richard Thurlow said they were extremely humbled when they learned about the kind gesture.
"The funds generated over the 15 years covered a significant dent in our operational costs. These are the patient-facing costs of the organisation, especially salaries," he said.
"This year it will cost $7.6 million to serve the Western Bay of Plenty community, and $3.7 million of this will come from fundraising."
Thurlow said the Waipuna Hospice Foundation, a separate trust to the operational part of the organisation, would invest the capital from the estate of Josephine Parish to ensure her legacy endures.
"As a not-for-profit we don't receive funds of this magnitude very often. This type of donation and bequest allows us to plan for the long-term and to build a fund to ensure future services for our community."
Every year, Waipuna Hospice serves around 1000 patients and families and that figure is forecast to grow, with a predicted increase of 75 per cent in the next 20 years.
The Trust of Josephine Parish was managed by Perpetual Guardian.
Perpetual Guardian client manager Sue Bacon visited Waipuna Hospice to present the large donation in person.
"It was an honour to present this on behalf of the Parishes. It is a prime example of how strategic funding can really make a difference to communities.
"The hospice does such a great job at providing support and care; it is a vital part of the community and would not be able to survive without donations like this one, which is much deserved."
The Parishes immigrated to New Zealand from England and Mr Parish was a teacher in Auckland for several years before the couple retired to Ōmokoroa.
They had no children and when Mr Parish became ill, Waipuna Hospice stepped in to help.
The organisation relies on government funding and community support to provide its services free of charge.