Who is sharing these expenses?
Enter the two names once. You'll pick from these when adding an expense.
Expense sheet
Add an expense in the blank bottom row: today's date is filled in (tap it to change), then what it was for, where, the amount, who paid and any remarks, and it saves itself a moment after you've entered the amount (Enter or Add saves straight away). Any change to a row saves automatically as you type. Balances assume every cost is shared equally.
Who owes whom
Balance = paid − share. Positive: others owe them. Negative: they owe others.
Settings
Everything is shared: changes by either person appear for both within a few seconds.