Your registration and CTP Green Slip are inextricably linked. You must have a CTP Green Slip policy in place before your registration is valid, but your car needs to be registered in order for your CTP insurance to be valid.
It is very easy to drive your car and not realise that the rego is overdue.
If you get pulled over by police, you may receive a large fine. However, you could get involved in a motor accident resulting in someone ending up being seriously injured or even killed.
There would not only be emotional and legal ramifications for this, but also a financial aspect to consider eg- fines and being sued. This is why Compulsary Third Party Insurance (CTP Green Slip) is mandatory in all Australian states.
How long after your registration expired do you have to renew?
There is no grace period – once your rego has expired, your policy is invalid immediately.