The design of monitoring systems and the methods used to transfer data between beneficiaries and managing authorities are not prescribed. Nevertheless, there are some minimum requirements in terms of the need to store micro-data for all participants, the annual reporting schedule, and the need to ensure quality of data (see section 2 in Annex D of the EG guidance on monitoring and evaluation).
In terms of transferring cumulative data between beneficiaries and managing authorities then whether or not this is a reasonable approach depends on what is transferred. If a full set of micro-data covering all participants to date is transferred then there should be no problem as the managing authority can prepare data for annual reporting purposes based on the start/end dates associated with each participation record and perform checks to identify any revisions to previously reported data and ensure the appropriate treatment. If only cumulative aggregates are provided then, in theory, annual figures can be derived each year by subtracting the values sent in previous years but there is then no obvious way to check for revisions. Unless suitable procedures are put in place to ensure that any revisions to previously reported data are appropriately identified and treated then this approach is unlikely to satisfy basic requirements for data quality.