When can my child move to a booster seat?
Types, legal minimum vs best practice, and fit. The 5-step test is for leaving the booster — not starting one.
Call 0479 168 579“Is my child ready for a booster yet?” is one of the questions we hear most. The honest answer is: usually later than you think.
Turning four does not automatically mean a lap-sash booster. Victorian (and national) road rules set a minimum. Best practice is to stay in a full harness until this seat’s booster marker is genuinely met — and the child can sit still.
The 5-step test is a different milestone. It is how you decide when a child can leave the booster and use an adult lap-sash belt alone. Do not use it to decide when to start booster mode.
The three types of booster
1. Convertible booster (Type B/E)
One shell, two jobs: a harnessed forward-facing seat, then booster mode after the child has passed that seat’s booster-mode shoulder marker. The internal harness is packed away; the car’s lap-sash belt does the work.
2. Tethered (dedicated) booster
Booster only. Sash guide, adjustable headrest, and a top tether. Everyday seat for a child who has already left a harnessed restraint.
3. Untethered “sometimes” booster
The light “bum booster”. No top tether (typically under 2 kg). Fine for a taxi or a grandparent’s car now and then — not the everyday restraint.
Legal minimum vs best practice
In Victoria, a child may use an approved booster from four years if they also meet that seat’s booster-mode shoulder marker. From four to under seven, the law allows a harnessed forward-facing seat or a booster. From seven, a booster or a well-fitting adult belt is legal — safest is usually still a booster until the 5-step test is passed in that car.
On many Type B/E seats built to AS/NZS 1754, the Standard places two forward-facing markers on the shell: a lower marker for the start of harnessed forward-facing (around 290 mm on the seat), and an upper marker for the start of booster mode (often in the 405–435 mm band). There is a small tolerance either side. Always read this seat’s labels and manual — marker height is not identical on every model.
Best practice: keep the 6-point harness as long as the current seat allows, often to about 7–8 years on a Type G, rather than switching at the fourth birthday.
Why Type G is often the better next step
A Type G seat keeps a full 6-point harness instead of moving straight to a 3-point lap-sash booster. The child cannot wriggle the sash behind their back, tuck it under an arm, or lean out after a dropped toy as easily.
At BebaBaby that usually means the Britax Maxi Guard or Infa Secure Emerge — then a dedicated booster such as the Kid Guard when the harness is genuinely outgrown. See car seat consultation or mobile fitting.
Before you switch
- At least four years old.
- Past this seat’s booster-mode shoulder marker.
- Can sit still for a normal trip.
- Will leave a dropped toy on the floor rather than dive after it.
If any answer is no, stay harnessed even if the legal minimum is met.
Getting booster mode right
- Internal harness packed away and unused.
- Lap-sash follows the marked (often red) belt path.
- Sash through the headrest sash guide.
- Lap belt low — usually under the armrest — both lap and sash together under the other armrest where the seat requires it.
- Top tether on, no slack — except a sub-2 kg “sometimes” booster that is not designed for a tether.
Anti-submarining
In a hard stop a child can slide forward under the lap belt. In our fittings, Infa Secure uses padding/pummelling and Britax uses a dedicated anti-submarining clip (built in or at the buckle). Use whatever that model specifies. See common installation mistakes.
Not sure they are ready?
We will check markers and belt path in your car across Bayside and the South East.
Booster seat FAQs – When Can My Child Move to a Booster Seat?
Can my child move to a booster at 4? +
Is the 5-step test how I know they can start a booster? +
What is a Type G seat? +
Do I still use the top tether in booster mode? +
What is submarining? +
Can you check if they are ready? +
General safety information only. Follow your seat manual, the vehicle handbook and current Victorian Road Rules. Marker positions vary by model. The 5-step test is for moving from a booster to an adult seatbelt, not for starting booster mode.