In its end-of-year update into over-charging and breaking of contracts over tracker rates by the industry, the regulator said the lenders under investigation had so far identified 8,200 accounts.
It expects 10,000 people will have been found to have been wronged when the probe is completed.
Knowledge of the scandal first publicly surfaced when Permanent TSB (now 75%-owned by the State) set aside tens of millions in its accounts for a redress scheme in the run up to a shares sale.
It subsequently revealed, in July 2015, that a number of customers had lost their homes because of its mistakes.
No deliberate policy of overcharging was found however, and Permanent and its former Springboard unit were fined.
For the first time yesterday, the Central Bank named the list of 15 lenders which it had written to a year ago, but did not explain fully why it hadn’t published the list beforehand.
The list includes AIB and its EBS and Haven units; Bank of Ireland; Dilosk; Permanent TSB and its former Springboard unit; Ulster Bank; KBC; Danske and Pepper Asset Servicing; ACC; Bank of Scotland; Irish Bank Resolution Corporation; Leeds Building Society; Start Mortgages and Stepstone.
“All lenders are progressing the tracker examination, however, each lender is at a different stage in the process ... for example, due to the number of mortgage accounts, the nature of the systems and records they have maintained as well as the different issues arising during the review,” the Central Bank said.
AIB has apologised and Bank of Ireland said last week its tracker mortgage redress investigations had identified 602 accounts where “a right to, or the option of, a tracker rate of interest was not provided to the customer in accordance with their loan documentation”.
Earlier this month, Ulster Bank said about 15 customers had lost their homes due to being denied the correct mortgage interest rate.
It said it had identified 2,000 wronged customers so far.