27 It should also be added that the reference to the national provisions designated by private international law in Article 4, paragraph 1 of Directive 2000/35 relates to the conditions of validity of the property reserve. 3) “property reserve”: the contractual agreement under which the seller retains ownership of the goods in question until the price is fully paid; Property reserve clauses must obtain the right of sellers to their goods, often until the full payment of the purchase price, and are often included in the terms and conditions of sale. In the case of cross-border transactions, it can be particularly difficult to know whether a property reserve clause is applicable. The property reserve is enshrined in national or heritage law, as well as in security and insolvency law, making harmonization extremely difficult. 19 According to the Italian Government, the purpose of the obligation to confirm the property reserve clause in documents attesting to the subsequent performance of the original contract is, among other things, to respect the principle of legal certainty and to protect third parties who have a commercial relationship with a party owned by a party owned by another party. 22 In order to determine whether the Commission`s application is justified, Article 4, paragraph 1 of Directive 2000/35 should be examined and whether this provision affects the provisions adopted by a Member State with regard to the applicability of property reserve clauses to third parties. “In the case of a sale on installment credit terms with property reserve, the buyer takes possession of the deal at the time of payment of the last tranche of the price, but bears the risks inherent in the case when the price is delivered.” “The property reserve under Article 1523 of the Civil Code, provided for by a prior written agreement between the buyer and the seller, is enforceable to the buyer`s third-party creditors when confirmed on individual invoices for successive deliveries with a specified date prior to a seizure procedure and duly recorded in the accounting documents.” 15 The obligation to confirm the property reserve clause on each invoice, in order for this clause to be enforceable against the buyer`s creditors, is tantamount to imposing on the seller an additional requirement which, in order to retain ownership of the goods until the full payment of the price, is only necessary under Directive 2000/35 for that clause to be compatible with the purchaser before the delivery of those goods.