Here's a basic guide for determining when to move up.Children who have outgrown car seats should be in a booster seat until they are at least 8 years old, or are 4’9” or taller.
For infants, from birth to at least 1 year old and at least 20 pounds, you should use a rear facing car seat.
For Toddlers, 1 to 4 years old and 40 pounds, you should use a forward-facing car seat.
Safety Belts should only be used when the child has reached the age of at least 8 years old, or a height of more than 4’9”.
There are a ton of options out there for the booster seat option. Some have the latch system, and some do not. Currently I can find any guidelines that say the latch is necessary once you're little one has gotten to the booster seat stage.
Why do I need to use a booster?
Safety belts are not designed for children. Beginning at around age 4, many children are too large for toddler seats, but too small for adult safety belts. A booster seat raises your child up so that the safety belt fits right and can better protect your child. The shoulder belt should cross the child's chest and rest snugly on the shoulder, and the lap belt should rest low across the pelvis or hip area – never across the stomach area.
You can find out more detailed information on the American Academy of Pediatrics web site at: