I have a CD that matured 12/07/2013. The 10 day grace period ended 12/17/2013. Customer closed the CD on 12/18/2013. Was an early withdrawal penalty of at least seven days interest required to be charged?

Not necessarily. You count from the rollover date, which was 12/7, so the closeout date fell after the mandatory regulatory penalty period (which would have been waived because it's in the grace period). So the closeout came when the bank had the legal and regulatory option to waive any penalty.

Thanks for your help.