I suddenly found a scratch on the back of my car, which should not have been caused by myself. I didn't notice it when I picked up the car. What should I do now ?

Try to explain directly to the staff who pick you up. Of course, looking innocent is a must. There is a chance to make it through. But when renting a car, you need to get used to taking photos of the four corners and front and back. Don't be lazy and skip this step.

If the scratch is not obvious, just ignore it. If it's serious, take a picture and leave a note when you return the car.

All that is covered by insurance is not very important.