Please be aware this information is specific to domains alone, this bears no relation to hosting accounts.
You can prevent a domain from being renewed by disabling Auto Renew. This is carried out via your account ( https://my.netnerd.com/clientarea.php ) by clicking on:
Domains > My domains > Click the spanner icon on the same line as the domain you do not wish to renew > Auto Renew > Disable Auto Renew
How Auto Renew functions:
If you disable Auto Renew on a domain, no invoices or notifications will be generated by us specific to the renewal of the respective domain.
Due to the above, if you disable Auto Renew on a domain and intend to renew it in the future, this dictates the need for you to fully monitor a domain's expiration date and manually renew domains (that have Auto Renew disabled) prior to a domain's expiration date being reached.
To renew a domain with auto renew disabled via your account:
Domains > Renew domains > Select the renewal period on the same line as the domain you want to renew > Add to cart > View cart > Complete the checkout / payment process.