Methods and apparatus, including computer systems and program products, for enabling the use of machine-readable codes. A computer program receives data generated by reading a machine-readable code and detects the presence of formatting information indicating whether the data's payload is in a first or second format. The program uses a first or second procedure to decode the payload depending on whether the formatting information is detected and what it specifies. In some embodiments, the formatting information can include information about how to decode the payload. The machine-readable code can have been produced according to an encoding instruction associated with an electronic document. The first and second formats can be open and closed formats, respectively. The use of multiple formats can enable multiple, co-existing business models in a document workflow, whereby different parties in the workflow can be charged or required to obtain authorization for the use of machine-readable codes.