Irish Nationwide boss Michael Fingleton will have to step down from the board after this weekend as he is turning 70, but he will remain as chief executive.
The move means that he will not be a board member of the building society, which is currently on the block, when it is finally sold.
Under the mutual's rules, directors must retire from the board once they reach 70, which Mr Fingleton intends to do.
However, the rules do not prevent a person of that age or older continuing to serve as chief executive, and a spokesman confirmed Mr Fingleton intends staying on in this post.
Irish Nationwide is one of just two building societies left operating in the Republic, but it is likely to be ultimately demutualised and sold.
It has been on the market since last year, and attracted the interest of Icelandic bank Landsbanki, property developer Quinlan Private and Bank of Scotland (Ireland), among others.
However, towards the end of last year it was reported that the interest of a number of bidders had cooled as the Republic's quoted banks had lost almost 40 per cent of their value on the stock exchange.
