(15)In order to ensure efficient and effective market monitoring, transaction reports should be submitted only once and to a single competent authority that can route them to other relevant competent authorities. Therefore, where an investment firm executes a transaction, it should submit the report to the competent authority of the home Member State of the investment firm irrespective of whether or not a branch is involved, or whether the reporting firm executed the transaction through a branch in another Member State. Moreover, where a transaction is executed wholly or partly through a branch of an investment firm located in another Member State, the report should be submitted only once to the competent authority of the home Member State of the investment firm unless otherwise agreed by the competent authorities of the home and the host Member State. In order to ensure that competent authorities of host Member State can supervise the services provided by branches within their territory, they need to receive transaction reports on the activities of branches. For this reason, and to allow for the transaction reports to be routed to all the relevant competent authorities for the branches that take part in those transactions, it is necessary to include granular data on branch activity in the reports.