OPINION 11. We have audited: (a) the accounts of the Joint Undertaking which comprise the financial statements (8) and the reports on the implementation of the budget (9) for the financial year ended 31 December 2017, and (b) the legality and regularity of the transactions underlying those accounts, as required by Article 287 of the Treaty on the Functioning of the European Union (TFEU). Opinion on the reliability of the accounts 12. In our opinion, the accounts of the Joint Undertaking for the year ended 31 December 2017 present fairly, in all material respects, the financial position of the Joint Undertaking at 31 December 2017, the results of its operations, its cash flows, and the changes in net assets for the year then ended, in accordance with its Financial Regulation and with accounting rules adopted by the Commission’s accounting officer. These are based on internationally-accepted accounting standards for the public sector. Opinion on the legality and regularity of revenue underlying the accounts 13. In our opinion, revenue underlying the accounts for the year ended 31 December 2017 is legal and regular in all material respects. Basis for a qualified opinion on the legality and regularity of payments underlying the accounts 14. The ECSEL Joint Undertaking has taken over the FP7 projects of the ARTEMIS and ENIAC Joint Undertakings. The payments made for these projects by the ECSEL Joint Undertaking in 2017, against certificates of acceptance of costs issued by the national funding authorities (NFAs) of the ECSEL Participating States, amounted to 76,4 million euro (2016: 118 million euro), which represents 32 % (2016: 54 %) of the total operational payments made by the Joint Undertaking in 2017. 15. ex-post audits of FP7 project payments on behalf of the Joint Undertaking. The ARTEMIS and ENIAC Joint Undertakings’ ex-post audit strategies relied heavily on the NFAs to audit project cost claims Administrative agreements concluded by the ARTEMIS and ENIAC Joint Undertakings with the NFAs have continued to apply since those Joint Undertakings were merged to form the ECSEL Joint Undertaking. Under these agreements, the NFAs performaudits of FP7 project payments on behalf of the Joint Undertaking. The ARTEMIS and ENIAC Joint Undertakings’audit strategies relied heavily on the NFAs to audit project cost claims ( 10 ) 16. The ECSEL Joint Undertaking has taken steps to assess the implementation of ex-post audits by the NFAs and has obtained written statements from the NFAs declaring that the implementation of their national procedures provides reasonable assurance on the legality and regularity of transactions. However, the significant variation in the methodologies and procedures used by the NFAs does not allow the ECSEL Joint Undertaking to calculate a single reliable weighted error rate or a residual error rate. 17. ex-post audits are functioning effectively and whether this key control provides sufficient assurance as to the legality and regularity of the underlying transactions for FP7 projects Therefore, the Court is not in a position to conclude whetheraudits are functioning effectively and whether this key control provides sufficient assurance as to the legality and regularity of the underlying transactions for FP7 projects ( 11 ) 18. ex-post audit ex-post audit of a random sample of Horizon 2020 interim cost claims of which the results, however, will only be reported in in the Joint Undertaking’s annual activity report 2018. This issue concerning the variation in the methodologies and procedures used by the NFAs is not relevant for the implementation of Horizon 2020 projects, as the Common Audit Service (CAS) of the Commission is responsible for theaudit ( 12 ) . In 2017, the Joint Undertaking — together with the Common Audit Service (CAS) of DG RTD — launched the firstaudit of a random sample of Horizon 2020 interim cost claims of which the results, however, will only be reported in in the Joint Undertaking’s annual activity report 2018. Qualified opinion on the legality and regularity of payments underlying the accounts 19. In our opinion, except for the possible effects of the matters described in paragraphs 14 to 18, payments underlying the accounts for the year ended 31 December 2017 are legal and regular in all material respects. Responsibilities of management and those in charge of governance 20. In accordance with Articles 310 to 325 of the TFEU and the Joint Undertaking’s Financial Regulation, management is responsible for the preparation and presentation of the accounts on the basis of internationally-accepted accounting standards for the public sector and for the legality and regularity of the transactions underlying them. This responsibility includes the design, implementation and maintenance of internal control relevant to the preparation and presentation of financial statements that are free from material misstatement, whether due to fraud or error. Management is also responsible for ensuring that the activities, financial transactions and information reflected in the financial statements are in compliance with the authorities which govern them. The Joint Undertaking’s management bears the ultimate responsibility for the legality and regularity of the transactions underlying the accounts. 21. In preparing the accounts, management is responsible for assessing the Joint Undertaking’s ability to continue as a going concern, disclosing, as applicable, matters related to going concern and using the going concern basis of accounting. 22. Those charged with governance are responsible for overseeing the entity’s financial reporting process. Auditor’s responsibilities for the audit of the accounts and underlying transactions 23. Our objectives are to obtain reasonable assurance about whether the accounts of the Joint Undertaking are free from material misstatement and the transactions underlying them are legal and regular and, on the basis of our audit, to provide the European Parliament and the Council or other respective discharge authorities with a statement of assurance as to the reliability of the accounts and the legality and regularity of the transactions underlying them. Reasonable assurance is a high level of assurance, but is not a guarantee that an audit will always detect a material misstatement or non-compliance when it exists. These can arise from fraud or error and are considered material if, individually or in the aggregate, they could reasonably be expected to influence the economic decisions of users taken on the basis of these accounts. 24. An audit involves performing procedures to obtain audit evidence about the amounts and disclosures in the accounts and the legality and the regularity of the transactions underlying them. The procedures selected depend on the auditor’s judgment, including an assessment of the risks of material misstatement of the accounts and of material non-compliance of the underlying transactions with the requirements of the legal framework of the European Union, whether due to fraud or error. In making those risk assessments, internal control relevant to the preparation and fair presentation of the accounts and legality and regularity of underlying transactions is considered in order to design audit procedures that are appropriate in the circumstances, but not for the purpose of expressing an opinion on the effectiveness of internal control. An audit also includes evaluating the appropriateness of accounting policies used, the reasonableness of accounting estimates made by the management and the overall presentation of the accounts. 25. For revenue, we verify the subsidy received from the Commission and assess the Joint Undertaking’s procedures for collecting fees and other income. 26. For expenditure, we examine payment transactions when expenditure has been incurred, recorded and accepted. This examination covers all categories of payments (including those made for the purchase of assets) at the point they are made. 27. In preparing this report and Opinion, we considered the audit work of the independent external auditor performed on the Joint Undertaking’s accounts as stipulated in Article 208(4) of the EU Financial Regulation ( 13 )