* No tengo la tarea: This is the most common and straightforward translation. It's suitable for most situations.
* No hice la tarea: This translates to "I didn't do the homework." Use this if you're admitting you didn't complete the assignment.
* No tengo la tarea hecha: This means "I don't have the homework done." It's a slightly more formal way of saying you haven't finished it.
* No he terminado la tarea: This translates to "I haven't finished the homework." Similar to the previous option, but emphasizes the unfinished state.
The best option depends on what you want to convey. If you simply haven't brought it to class, "No tengo la tarea" is perfect. If you haven't completed it, one of the other options would be more appropriate.