Duo tracks shared child expenses between two parents — school, doctor, clothes, food, activities. Both parents see the same ledger: who paid, how much, what for. Duo splits by your agreed ratio (50/50, 70/30, custom) and shows running balance. No bank linking, no public feed, no judgement. Just a clean ledger between two co-parents. Duo Plus unlocks PDF/CSV export (useful for legal documentation), push notifications, and email reminders. One sub covers both parents.