You need to tell them, especially if the car is modified in another way. If you're in an accident or get pulled over driving a lowered car with alloys wheels or whatever and the rear seats are out, excuses won't always cut it. Especially if you're caught twice
Luckily enough, it's usually pretty cheap! I'm with Bell and they didn't charge a penny more.
Really? What insurer woul charge more in all honesty? I can understand alloys or performance mods but taking your seats out isn't gonna change anything other than your passengercarrying capacity...