EMERSON Article ~ more details (forward-facing)

Here's another detailed post. In this one I talk about forward-facing.

FORWARD FACING
Most forward-facing carseats used to have a maximum-harnessed weight limit of 40lbs, after which you would be required to move your child to a booster seat, regardless of height or age. This was "fine" if you had a light child, but many kids hit 40lbs at 3 years of age (or sooner!)

There are now many options available which will allow you to keep your child harnessed up to 47, or even 65lbs. A 5-point harness is the safest option for your child, and it is recommended to keep them in the 5-point harness to the maximum weight/height limit of the seat. When buckling your child, the chest clip should be at armpit level, the straps should be untwisted, and lay flat, and the harness should be snug enough that you can’t pinch any slack in the webbing. You should be able to fit only 1 finger between the webbing and your child’s chest.