Letting accounts or domains expire

This vulnerability type is an easy trap to fall into. Companies need a domain and sometimes accounts at third party providers such as payment service providers. All of these services are not free of course, they cost money and normally companies will often opt to pay yearly for these services as they get a discount. However if the payment details of the company change and they do not remember to update them, their automatic renewal will not continue. This is especially easy to forget on domains and accounts that are not often used.