With Auto Charge On Due Date switched on, when the daily past-due job finds the proposal still unpaid after Due Date + Net Days it attempts to charge the outstanding balance to the customer's saved Stripe card automatically (the customer attached to that proposal). On success a payment is recorded, the proposal becomes Fully Paid and your kitchen email receives the fully paid notification. On failure the proposal is flagged with an auto-charge error: a red "Error In Auto Charging This Proposal: …" banner appears on the proposal, and in the current code it is listed in the auto-charge errors panel on the Events page only while the proposal itself was created within the last 7 days (the panel filters by the proposal's creation date, not by when the error occurred) — the customer and your kitchen email get the auto-charge error emails, and any proposal team members are notified regardless of whether it shows in that panel. The flag clears automatically the next time any payment succeeds on that proposal.