(53)Where detergents and end-user surfactants coming from third countries are placed under the customs procedure of release for free circulation, the reference to a digital product passport for those detergents and surfactants should be made available to the customs authorities by the economic operator. Such reference should correspond to a unique registration identifier communicated to the economic operator by the registry. Customs authorities should verify as a minimum that the unique registration identifier and the relevant commodity code for the detergent or end-user surfactant provided or made available to them correspond to the data that are stored in the registry. This would allow customs authorities to verify that a digital product passport for imported detergents and surfactants exists. To carry out that automatic verification, the interconnection between the registry and the EU Customs Single Window Certificates Exchange System should be used.