Car seat recline

Je

Is your baby's car seat still reclined? When must we put it in the upright position? In my husband's car, it is fully upright and the baby does great. In my car, the car seat is still fully reclined (baby does not complain!).

Must I straighten the car seat in my car? If so, when? I know that I *can* straighten it, but I'm trying to find out if I have to. Google was surprisingly unhelpful. Baby is rear facing of course.