Michael O'Sullivan, from Stoneybatter, north Dublin, has told how the pair have chose to tie the knot next month in a ceremony in Tipperary.
Michael O'Sullivan acts as carer for his friend Matt, who wants to give him his home when he dies.
AFTER TWENTY-NINE years of being best friends, two Dublin men in their 80s have made a decision to get married.
The neighbours, Matt and his neighbour Michael O'Sullivan, have planned to get married before Christmas.
Asked why he was marrying his best friend, Matt replied: "Because he'll be part of my life when I die and whatever I have in my home he can have without any problems".
"It's a way to avoid tax. I thought it was a very good thing that came into my head to say, nowadays, this is official".
Those in the Republic of Ireland who are married are exempt from inheritance tax on property from their partner.
"I never married, he was married and has a talented daughter in London, he had another partner and another daughter and son with them". They are officially coming together purely for tax purposes. "With the house, this is the easiest way", said Matt.
Duffy asked him what would happen if Michael met a woman but Matt said his friend has assured him that even if he did, he was happy to remain as a just partners with any potential new love.
Mr O'Sullivan also spoke to "Liveline" and explained that he and Matt had known each other for a very long time.
"I know Matt 29 years, the same age as my own daughter, and he lives in the same area".
"He's one of the nicest people that anyone will ever meet in your life".
The reason for doing so is to ensure that Michael would be able to inherit Matt's house without having to pay any Capital Acquisition Tax.