TSB Bank is moving its former Northern Rock portfolio to a new brand called Whistletree.
Whistletree has been set up to give the former Northern Rock customers a distinct home within TSB.
TSB bought a portfolio of mortgages and other loans from Cerberus Capital Management in November 2015.
But before Whistletree, UK Asset Resolution handled these customers.
TSB customer service operations director Padraig Carton says: “We are delighted to welcome these customers to Whistletree from today.
“Whistletree will provide a secure, long-term home for these mortgages and loans based in the UK.”
TSB is writing to its customers this week about the change.
The move to Whistletree will not affect current loan agreements.