If your district reuses teacher IDs, it is best to send us a list of ID numbers for teachers who have left the school before you run imports. That way we can disable the IDs in our system so they can be used again. Click the red Help link at the top right of your portal to send us a help ticket listing the ID numbers to be recycled. If you've already run imports with the recycled ID numbers, you may have difficulty registering the new teacher accounts. In this case, contact support with a list of the recycled  ID numbers along with the names of the old and new teachers associated with each number and we'll fix it up for you.