If my company is handling both sustainable and non-sustainable stock, should both be registered in the UDB, or only sustainable stock?

Only sustainable material will be traced on the UDB, except in the case of blending.

With regard to sustainable fuel, only those consignments reported on the UDB (by fuel producers) and further sold to fuel suppliers on the UDB will be available to the final fuel supplier to mark the fuel as consumed in the market. Offline reporting of consignments put on market will not be allowed on the UDB as this defeats the purpose of the UDB from a traceability perspective and will lead to double counting/ irregularities. Economic Operators would have the report of all consignments put for consumption by final fuel suppliers on a real-time basis. Additionally, an annual report can be extracted by both Economic Operators and EU Member States for sustainable fuel.