819.03 Adding a Class During Examination 
Amendments to classification are rare in TEAS Plus applications, since the identification of goods/services is taken from the USPTO ID Manual, and the TEAS Plus form does not permit the applicant to edit the "Classification" field. In the rare case where the TEAS Plus applicant amends the application to add a product or service that is within the scope of the original identification of goods/services, but is in a different class, the fee for the additional class is the reduced TEAS Plus fee, as long as the amendment is filed through TEAS or entered by examiner’s amendment. See TMEP §1403.02(c).
Example: The applicant selects the identification "hair shampoo" in Class 3. The applicant later adds "dandruff shampoo" in Class 5, which is within the scope of the original identification. The applicant will pay the reduced TEAS Plus fee, as long as the applicant has not lost TEAS Plus status for some other reason.
If the applicant adds a class after losing TEAS Plus status, the applicant must pay the regular TEAS fee if the fee is paid through TEAS or by examiner’s amendment, or the paper fee if the class is added by a paper amendment.