If you are under a contract and you need to cancel service, you may be subject to an early termination fee (ETF).
If you move to a Comcast serviceable area, and transfer service, you are not charged.
If you move to a Comcast serviceable area, and do not sign up for service, then the ETF would apply.
If you move to a non-Comcast serviceable area, then the ETF does apply.
If it is an active duty military deployment, then the ETF will be waived when you send documentation.
If the account holder is deceased, the ETF will be waived upon receiving a death certificate or obituary.
If you downgrade service, then the ETF will not apply.
If you have a Double/Triple Play and remove all but one service, then the ETF will not apply.
Not sure if you are under a contract?
Visit my.xfinity.com from your web browser and select the My Account tab.
Sign in using your XFINITY username and password.
Click the Settings tab.
Click the Legal Agreements & Contract link under Account Details on the left-hand side of the screen.
Click the View link to see more details about your contract and/or legal agreements with Comcast.
[Last edit 4/20/17 nerdburg]