A material change of use occurs when a council concludes that a property has stopped functioning as a normal home and started operating as visitor accommodation. There is no fixed threshold, but common indicators include high guest turnover, frequent arrivals and departures, noise or disturbance affecting neighbours, parking pressure, and refuse issues. The same property can be low-risk with occasional letting or high-risk with back-to-back bookings throughout the year, depending on how it operates in practice.