How it works
Each payment is split equally between the people it was for (everyone, if you don't tick anyone). A person's balance is what they paid for the group minus their share of everything: positive means they get money back, negative means they owe. To settle up, the person who owes the most pays the person owed the most, as much as one of them needs, and that repeats until everyone is at $0. It never takes more than one payment fewer than the number of people. The spreadsheet does the same with uneven shares (one person paying double, for example), categories, budgets and a Paid? column.