Maker here. This started on a trip where five of us wanted to keep a shared kitty and the app everyone suggested wanted five sign-ups first. Two people never got around to it, so we ended up with a notes file and an argument at the end. So the constraint I set myself was: joining a pot must work with a link and nothing else. No account, not even for the person who gets invited. That turned out to be the hard part rather than the maths, because without accounts you have no identity to hang permissions on. What I landed on is a key stored on each device, which also means your payment details can be encrypted for one specific recipient instead of sitting on a server in plain text. It started on iPhone; since August the Android app is out too, and both can be in the same pot – which, it turns out, is what most mixed groups were missing. It's free. Pro is for the things I'd want myself on a longer trip: uneven splits, recurring expenses, receipt scanning, PDF export. Happy to answer anything, especially about the no-account part.

sharepot

Split group expenses on iPhone and Android. No account.

Split group expenses on iPhone and Android. No account.