The fund that will collect money from dormant bank accounts before it goes to the Big Society Bank has been given the go-ahead by the Financial Services Authority.
Reclaim Fund Ltd, which will be administered by Co-operative Financial Services on a not-for-profit basis, will collect all money held in dormant accounts in UK bank and building society accounts.
Some of that money will be held in the fund in order to be transferred to account holders who eventually claim their money.
The remainder will be passed on to the Big Lottery Fund for distribution to good causes. In England, all of the money will go to the Big Society Bank, which will act as a wholesale lender to retail social investors.
Cash from dormant bank accounts is expected to total about £400m, with between £60m and £100m available during the first year.
Setting up a reclaim fund is a necessary step to setting up the bank. But before the bank can be fully established, the government must still win an agreement from the European Union that the bank does not breach strict state aid rules.
Paul Mills, executive director of Reclaim Fund Ltd, said: "Our aims are very clear. While we will give as much money as possible to Big Lottery Fund for good causes, we will also be prudent in keeping back enough for customers who come forward to claim accounts they had forgotten about."