Where is the money held and who has access? (security)

Contributions to kin groups are held in the Kin Cooperative bank account. Kin banks with the Co-operative Bank. 

Wasn't the Co-operative Bank sold to private owners?
Yes, but! Following the 2008 financial crisis, the Co-operative Bank was bought by private equity but as of January 1st 2025, it has been purchased by Coventry Building Society and will be re-mutualised - that means owned by its members and users and not by private shareholders. 

Only a few members of the Kin Cooperative Team have access to the bank account and all contributions and gifts are checked and paid out and double checked manually.