Ulster Bank will tell the Oireachtas Finance committee tomorrow that 15 owner occupiers lost their homes due to the tracker mortgage controversy.
Ulster Bank will also say that the number of customers who lost their homes has not yet been finalised.
It is due to say that it is prioritising the identification and payment of redress and compensation to customers who lost homes.
It has also emerged that almost two third of Ulster Bank's mortgages are tracker loans.
This information has been disclosed in a questionnaire, seen by RTÉ News, ahead of the bank's appearance at the Oireachtas Finance Committee tomorrow.
The questionnaire shows that tracker mortgages account for 64% - or €11.2 billion - of Ulster Bank's portfolio of loans at June 2017.
Typically trackers lost banks money because customers were paying a lower interest rate than banks were being charged.
The heavy financial burden of trackers is suspected to be one of the main reasons banks wrongly moved customers from the mortgages.
Tomorrow Ulster Bank will tell the committee it has identified 3,500 mortgages which were impacted in the controversy.
The bank has been previously criticised by politicians for its slow progress in identifying the total number of affected customers.
Tomorrow outgoing chief executive Gerry Mallon will say that the bank is still working to identify any additional mortgage holders.
Ulster Bank will say that it has returned 2,500 customers to the correct rate. It has paid compensation to 1,017.
Mr Mallon will issue an unreserved apology for the failures. Ulster Bank has 200 staff working on the issue.
The questionnaire also asks Ulster Bank if it has identified which staff members or directors were authorised to deny customers trackers.
The bank has declined to comment and said the issue was subject of a Central Bank investigation.