When a bill quietly goes up 10% or more.
If a fixed bill's latest payment is 10% or more above its trailing average (up to 6 prior payments), you get a price-increase item in the notification center with the percentage. Variable bills are excluded by design.
Pure math on your payment history: the latest payment is compared to the average of up to six payments before it. At or above +10%, an alert appears in the notification center (bell icon) with the whole-percent change. One payment isn't a trend, so the average is doing the work.
Utilities and credit cards are supposed to move month to month — flagging them would be noise. Only fixed-amount bills are checked.
Open the vendor from the alert. On Pro, the vendor drawer gives you the cancellation link, call/email shortcuts, and a negotiation script — the three levers that actually lower the bill. If you keep the new price, edit the bill's expected amount so future totals stay honest.