You can close and/or delete your account by visiting your profile, clicking the 'Edit Profile' tab which is located below your 'Username' and then hitting the delete button. 
This will remove your profile from the site. 
You can also auto-ban your account for a certain period of time by clicking in the calender the date of your comeback.
As for the final cashout for the account, if this applies, please call our customer support center or request the final cashout before deleting your profile.