You can delete recurrences from either the original entry, or any entry that has recurred since you scheduled the recurrence.
From the daily history section of the time & sales screen, locate the time & sales entry you originally scheduled to recur, or any recurrence that has resulted from the scheduling. If you do not see the item in the list, you can always locate it by using the filtering/searching/sorting feature.
At the beginning of the entry's row, you will see the 
icon. Click it to delete the recurrence schedule.
Deleting a recurrence will not affect any existing entries, only the recurrence schedule. If you would like to delete an entry, use the
icon.
Once you confirm the delete, the recurrence schedule will be removed, and all future recurrences will stop.