This framework document is intended to be useful for facility operators required to report to a PRTR, by providing information on the general principles for estimation of releases at an industrial site; the applicability of the various release estimation techniques; issues that need to be taken into consideration when applying the techniques; and issues that would support the evaluation of the release data. The document is designed to assist PRTR project managers and policy analysts by providing an insight into the practical issues associated with the production of emission data on-site and the application of the bottom-up approach to estimation of releases.