Default Calendar reminders notifying when they shouldnt

Im using the builtin calendar and syncing the calendar with gmail and tasks with my samsung acct (since you cant sync tasks to gmail for some reason). ive done this so i can see everything on this tablet and my note3. the problem i have is, when i complete a task, i check the task off as completed but the reminder will still go off at its assigned time. for example, i have a task to pay a bill Dec 10. i have a due date on Dec 10 and a reminder set on Dec 10. Lets say i pay my bill today. i now mark this task complete. its checked and crossed out in the list as completed. On Dec 10, i get a reminder for this task still. i cant find an option to change this behavior. this same issue is present on my note 3. is this normal behavior for or am i missing a setting somewhere? i would think that a completed task should have its reminder set to not activate.
T-Mobile Galaxy Note 3
T-Mobile Sensation 4G, CM10 tossed in my camelbak for mtn biking so I don't hurt my Note2. LOL.
Galaxy Note 8.0
Galaxy Note 10.1 2014 Edition