The "whole loan" sale was acquired by E-Mex Home Funding, a subsidiary of Cheshire Building Society.
The transaction represents GMAC-RFC's fifteenth portfolio sale in the last three years. Other portfolio sales from GMAC-RFC have been acquired by a range of lenders that vary in size - from large high street names, to smaller building societies.
Commenting on the move, Stephen Hynes, capital markets director at GMAC-RFC said: "We are delighted that Cheshire Building Society has partnered with us for this portfolio acquisition and, as the leading all-status lender, we are looking to establish similar relationships with other clients. This type of sale is becoming increasingly popular in the UK mortgage industry and the creator and trader technique is revolutionising the market."
