If you'd like to cancel and not renew your domain please login to your client area. Once logged in click on Domains > My Domains. From the table of domains click on the tool icon on the right side of the row. You should see a page which gives you an Overview of the domain information. From the menu of links on the left side of this page click on the 'Auto Renew' link. On this next page you should see a red button labelled, 'Disable Auto Renew', click it. This will disable the auto-renew function and prevent any further invoices from being automatically generated for the domain. This allows for the domain to expire. Please note if a domain is cancelled you will not be billed for it any further and the domain will become available for someone else to purchase.