The firm, which won best remarketing company and best website awards, will remarket 30,000 cars every year for private dealership group Retail Automotive Alliance (RAA).
In one of the biggest deals of its kind, more than 30,000 vehicles will be offered each year by auction at eight of Manheim’s auction houses.
Formed just over 12 months ago, the RAA comprises 22 privately-owned dealer groups with a combined turnover of £2.4 billion.
It represents 165 dealerships and 14 franchises, and was formed to create more effective trading relationships, particularly in service supply.
Manheim’s sales director, dealers, Alan Cureton, said: ‘This is an exciting development as it really does give our buyers the best of both worlds.
‘Stock direct from franchise dealers is highly desirable and this new contract means we are able to market a combination of highly reputable dealer groups through one channel.
‘It’s inevitable that more buyers will follow the programme as we can offer much greater choice through a limited number of locations.
‘We can also still satisfy those regular buyers of stock from the individual members.’
The sale programme will be branded as RAA, but use the individual dealers to promote it locally.
RAA chairman Philip Maskell said: ‘This new contract with Manheim is exactly the sort of arrangement that generates benefits for our members.
‘We can create a marketing presence as a group which individual members would not be able to do on their own.
‘This allows us to combine all our part-exchanges and any non-required retail stock into one focused sale programme, ensuring Manheim is able to promote this stock in the most effective way.’
The Manheim auction centres taking part are Wimbledon, Colchester, Bristol, Birmingham, Mansfield, Manchester, Knottingley and Washington.
Details of the deal come weeks after BCA announced a £1 billion deal with Lex Vehicle Leasing.