Why it is harder than it looks
The register is not a list of vendors; it is a relational dataset with a dozen linked templates: entities, contracts, providers, services, functions, subcontractors. The difficulty is that the data lives in four places (procurement, legal, IT, the business) and that the supervisor validates the file structurally before reading it. Financial entities that built it in spreadsheets in the first year discovered that keeping it current is the actual obligation, not producing it once.
Living data, not an annual export
The register must reflect the current state of the arrangements, which means a new contract, a change of subcontractor or a reclassified function has to land in it when it happens. That only works if the register is a view over the supplier inventory, the contract records and the business function map the organization already maintains for its third-party risk program, so that the same fact is entered once and the export is generated on demand.
What it enables
Beyond the reporting duty, the register is what makes the rest of DORA’s third-party chapter operable: concentration risk can be measured only if the register shows which functions depend on the same provider; exit strategies are needed only for the arrangements it flags as critical or important; the oversight of critical ICT providers is designated from the aggregated registers of the sector. An entity that treats it as the backbone of its supplier data, rather than as a compliance file, gets the analysis for free.