Add each payment stage with its own label, amount, and due date. Tick "Paid" once the client actually pays it. Paid So Far and Balance Due below are calculated automatically from what's marked Paid here — there's no separate Advance field to keep in sync. Use the reminder bell to email the client about an upcoming due date — this happens automatically 7 days before, or you can send/resend manually anytime (only available once the client has been saved).