Apparently, opinions vary.
From the
Jackson County Sheriff's web site: Pursuant to Missouri Law, there is a $10 late penalty fee assessed for
each month the permit is not renewed, up to 6 months.
After 6 months,
the permit is invalid, and the holder must begin the application process
over again.
From
MO Legislature site: 4. A person who has been issued a concealed carry permit, or a
certificate of qualification for a concealed carry endorsement prior to
August 28, 2013, who fails to file a renewal application for a concealed
carry permit on or before its expiration date must pay an additional late
fee of ten dollars per month for each month it is expired for up to six
months.
After six months, the sheriff who issued the expired concealed
carry permit or certificate of qualification shall notify the concealed
carry permit system that such permit is expired and cancelled.
I've sent the Sheriff's office an inquiry via email.