125cc bike, 16 years old, cbt only, when can i carry a passenger?

Hi, ive been riding a scooter scine i was 16 and now im 17 im planning on getting i 125cc bike, when will i be able to carry a passenger?
ive only took a cbt and i know i can go straight on a 125 when im 17 with just a cbt will i be able to carry a passenger too or do i need to complete the motorbike test? thankyou x
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