When does liability of the common carrier commence in connection to the transfer of goods?

It begins with the actual delivery of the goods for transportation, and not merely with the formal execution of a receipt or bill of lading; the issuance of a bill of lading is not necessary to complete delivery and acceptance. (Compania Maritima v. Insurance Co. of North America, G.R. No. L-18965, Oct. 30, 1964)