iCal not syncing between Macbook and iPhone

On a regular basis (but not every time) if I have an event in iCal and I dismiss it on my iPhone, later in the day when I open my Macbook the even will still persist in notifications as if I hadn't taken care of it earlier. This occasionally happens with Reminders as well, but far less often. Does anyone else have this issue and is there a setting I am missing to get these to sync. Thanks in advance for any suggestions.