Mississippi Booster Seat Laws: Age, Fines, and Exemptions

Mississippi booster seat laws require every child aged four through six to ride in a belt-positioning booster seat unless the child is at least 4 feet 9 inches tall or weighs at least 65 pounds. The rule comes from Mississippi Code § 63-7-301, and a violation is a primary offense: an officer can pull you over for that reason alone, with no other infraction needed.¹

Which Children Need a Booster Seat

The booster requirement starts on a child’s fourth birthday and ends on the seventh. Within that window, the child must ride in a booster unless they have already outgrown both size thresholds. The statute covers children “at least four years of age, but less than seven years of age,” so a child who turns seven is no longer under the booster rule regardless of their height or weight.¹

The size exemption works on an either/or basis. A child in the four-to-six age range who hits 4 feet 9 inches tall OR 65 pounds has met the law and can legally ride in a standard seat belt. In practice, most children in this age bracket meet neither threshold, so plan on a booster for the full three years.

Meeting the legal minimum is not the same as being ready. NHTSA recommends keeping a child in a booster for as long as they fit within the manufacturer’s height and weight limits, even after they have aged out of the state rule. If a seat belt still rides up across the child’s neck or stomach instead of sitting flat across the chest and thighs, the child benefits from staying in a booster longer.²

What Counts as a Proper Booster Setup

A booster seat lifts the child so the vehicle’s lap and shoulder belts cross the right parts of the body. The shoulder belt should run across the center of the chest and over the shoulder, not against the neck. The lap belt should sit flat across the upper thighs, not riding up over the stomach.

Mississippi law requires the booster to be used with both the lap and shoulder belt. A lap-belt-only setup does not satisfy the statute, and tucking the shoulder belt behind the child’s back or under their arm would not be considered legal compliance during a traffic stop. The booster itself must also meet applicable federal motor vehicle safety standards, which any new seat sold in the United States will.¹

High-Back vs. Backless Boosters

State law doesn’t specify a style, so both high-back and backless boosters are legal as long as they meet federal standards. The practical choice depends on your vehicle seat. If the vehicle seat lacks a headrest or has one too short to support the child’s head, a high-back booster provides that support on its own. If the vehicle seat already has an adequate headrest, a backless booster works. Either way, the child should sit with their back flat against the seat and knees bent comfortably at the seat edge.

If You Have More Children Than Shoulder Belts

The statute addresses a common squeeze: a back seat with only two lap-and-shoulder belts and three or more children. In that case, the two children in the shoulder-belt positions must use booster seats. Any additional child may ride in a lap belt only. This exception applies only when every available lap-and-shoulder belt is already occupied by a booster-seated child.¹

Before Four and After Seven

A child younger than four must ride in a child passenger restraint device, which generally means a rear-facing or forward-facing car seat with an integrated harness. A booster seat alone does not satisfy the law for a child under four, regardless of the child’s weight.¹

Once a child ages out of the booster rule, Mississippi’s general seat belt law takes over and requires all passengers to be buckled in.³

Fines and What a Violation Does (and Doesn’t) Mean

Because the violation is a primary offense, an officer who sees an improperly restrained child can initiate a stop for that reason alone. The base fine is commonly reported as $25, with court costs added on top that vary by county and can push the total noticeably higher.

One protection is written into the statute itself: failure to use a child restraint cannot be treated as contributory or comparative negligence. If your child is injured in a crash and a civil case follows, the fact that the child wasn’t in a booster can’t be used to reduce your claim or shift fault to you. The traffic penalty stands on its own and doesn’t carry over into a lawsuit.¹

When the Rule Doesn’t Apply

The booster requirement applies to passenger motor vehicles on public roads. Vehicles that were never manufactured with seat belts under federal standards, such as school buses and farm equipment, fall outside the law’s scope.

Rideshare vehicles get a specific exemption under state law, so the booster rule is relaxed if you’re riding in an Uber or Lyft. Taxis do not appear to share that exemption. A standard seat belt is always safer than nothing, and bringing your own booster into a rideshare is still the better call when you can.

Mississippi’s general seat belt law also allows a medical exemption for passengers who cannot wear a belt due to a medical condition. The exemption requires written verification from a licensed physician, and you should keep that document in the vehicle in case you’re stopped.³

Getting Your Installation Checked

Buying the right seat is only half the job. Studies consistently find that most car seats have at least one installation error. NHTSA runs a Car Seat Inspection Finder that connects you with certified child passenger safety technicians, who will check your setup and show you how to fix problems, usually at no cost.⁴

Many Mississippi fire stations, hospitals, and law enforcement offices host car seat check events or have a technician on staff. Families enrolled in WIC, SNAP, Medicaid, or TANF may qualify for free or discounted seats through local community organizations, often paired with hands-on installation training. Your county health department is a good first call.