20 CFR § 10.702 - How are fees for services paid?
(a) A representative may charge the claimant a fee and other costs associated with the representation before OWCP. The claimant is solely responsible for paying the fee and other charges. The claimant will not be reimbursed by OWCP, nor is OWCP in any way liable for the amount of the fee. Contingency fees are not allowed in any form.
(b) Administrative costs (mailing, copying, messenger services, travel and the like, but not including secretarial services, paralegal and other activities) need not be approved before the representative collects them. Before any fee for services can be collected, however, the fee must be approved by the Secretary.