For the Great North Run only, if an entrant decides not to run, they are entitled to withdraw their entry and receive an opportunity to buy a guaranteed entry the following year's event without having to apply through the ballot system (defer their entry). 

You will need to pay the standard entry fee for your guaranteed place the following year. 

Once you’ve committed to defer your entry, you cannot be added back into the event.

You will be contacted in November with instructions of how to register and pay to secure your guaranteed entry into the following year’s event.

More details can be found here