How are balances worked out, and what does Simplify debts do?

The top of Groups shows what you are owed and what you owe across all your groups, archived ones included, and what is just between you and a friend, a line for each currency. Where that is in more than one currency, a line under it estimates the whole in your Default currency at the day's exchange rates; nothing is converted. Each group in the list shows where you stand in it, and Friends nets everything between you and each person across the groups you share.

Open a group and tap the line under its balance to see everyone's position and who pays whom to settle up. A positive amount means the group owes that person; a negative one means they owe the group.

Simplify debts works out the payments from what each person owes or is owed overall, rather than from who paid for whom, so money can be rerouted: if Ana owes Ben 20 and Ben owes Carla 20, Ana pays Carla directly. With it on, nobody both pays and gets paid. It never changes how much anyone owes or is owed overall, and each payment says how much of it was owed directly and how much was rerouted.

It is on for new groups. Turn it off in Group settings, or switch the balances screen between Simplified and Who paid for whom. Either way it changes the setting for everyone in the group.