About half of the 320 local Age Concerns have agreed to become brand partners with Age UK.
Age UK, which was formed by the merger of Age Concern England and Help the Aged two years ago, gave local Age Concerns until 31 March to decide whether to sign partnership agreements.
Brand partners will rebrand as Age UK and have the opportunity to enter into a trading alliance with the national body.
Helena Herklots, services director at Age UK, said 135 had agreed to join and another 40 applications were being processed.
She said she was pleased with the figure and that any charities that had not joined had until the end of October to become "friends of Age UK", an arrangement aimed primarily at the smaller Age Concerns that do not have the financial muscle to enter into a trading agreement.
Friend organisations would still be called Age Concern, providing they added "friend of Age UK" to their names.
"We always expected about half would become brand partners and about half would become friends of Age UK," said Herklots.
Age Concern Manchester this week became the latest Age Concern to say it would not join. "We need to keep our focus local," said chairman Stuart Murray.
Sixteen Age Concerns have become partners in a rival trading venture called Advant~Age, which was launched this week. Age Concerns in Birmingham, Liverpool, Cardiff and Hampshire are among those involved.
They are urging Age Concerns that have not become Age UK brand partners to join.