49 CFR §373.105

The carrier and shipper may elect to waive the above provisions and use a more streamlined recordkeeping or documentation system for distribution of “low value” packages. This includes the option of shipping such packages under the provisions of 49 U.S.C. 14706(c). The shipper is responsible ultimately for determining which packages should be designated as low value. A useful guideline for this determination is an invoice value less than or equal to the costs of preparing a loss or damage claim.