The Halifax has warned former members of the Birmingham Midshires Building Society they have three months to claim outstanding windfall shares and cash of up to £14.4 million sterling (€23.46 million).
At that stage, any outstanding shares will be sold.
The British financial institution placed an advertisement in The Irish Times yesterday aimed at former members of the building society possibly resident in Ireland.
An estimated 19,000 people have still not claimed free shares, collectively worth €12.38 million, distributed when Halifax bought the building society in April 1999.
A further 6,800 people have failed to collect cash of €11.08 million.
Halifax, part of the HBOS group, has warned that unless the shares are claimed by July 25th, they will be sold.
If you are unsure as to whether you are entitled to free shares or cash, contact the Birmingham Midshires information office on 0044 1902 325914 or visit www.askbm.co.uk.