The virtual permit system is a two-step process whereby you are required to successfully apply before you can purchase your permit. It is important that you do not get confused between the permit application and the permit session that you are required to purchase thereafter.
All permit applications are valid for one year and it is the application that enables you to purchase a permit session. You are able to purchase annual, three monthly (quarterly) or six monthly (half-yearly) permit sessions against your application. If you purchase three or six months, you are able to purchase another three/six months when that session expires under the same application. You are only able to purchase subsequent (rolling) sessions whilst there is still enough time (three/six months) remaining against your permit application.
If there are less than three/six months remaining before your application is due to expire you will need to renew the application to continue purchasing quarterly or half-yearly sessions.