There is a way for users to use two similar Task Codes without receiving the duplicate error message.
When creating a "New Task Code" under Time>Settings>Task Codes, you will see a field for "UTBMS Code". Insert the duplicate code here.
For example, enter "B100 - Administration" and then enter a description in the "Description" field to differentiate the two codes you have in there.
Note: In the first field, you would still have to enter a unique code, for example "B1261".