Now, in this online world, there may be nothing "physical" in your house to tell your next of kin that you have a Monzo account, so they may never know, and your beneficiaries may never get that money - eventually the bank would close the account and put the funds into a "frozen"/suspense account which would languish potentially for decades
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Your next of kin or executor can't be contacting every potential financial institution - there are hundreds of them!
I can't help thinking there should be a system whereby a list of deceased persons is maintained and financial institutions regularly - I don't think it would need to be any more than monthly - check this against their client list. I don't think it would be especially onerous for the financial institution to implement this, speaking as a software developer working for a financial institution.