OceanaGold : 2023 RGMP Implementation and Conformance Report

2023 Responsible Gold Mining

Principles Implementation and

Conformance Report

April 2024

Introduction and commitment to the Responsible Gold Mining Principles

At OceanaGold Corporation (OGC) we are committed to mining responsibly. We endeavour to undertake our activities with respect for the environment and the human rights and wellbeing of our employees, contractors and members of the communities associated with our activities. We believe that coupled with good governance, responsible mining delivers benefits for host countries and local communities. It contributes to socio-economic development through increasing prosperity, providing jobs and supply chain opportunities, and raising technical standards through innovation and building skills.

OceanaGold takes this commitment seriously and as such, has committed to the implementation of, and ongoing conformance with, the World Gold Council's (WGC) Responsible Gold Mining Principles (RGMPs or Principles) to ensure the key elements of responsible gold mining are embedded in the way our Company operates.

This RGMP Implementation and Conformance Report summarizes how OGC has conformed with the requirements of the RGMPs for the year-ended 31 December 2023 and is a final requirement of formalizing assurance of our conformance with the WGC's RGMPs.

Assurance of our conformance is provided by Bureau Veritas (BV) and follows this Report as an Appendix. In conforming to the Principles, we have:

• Developed, implemented, and maintained policies, systems, processes and controls to ensure that the Company conforms with the Principles;
• Disclosed information that helps external stakeholders understand how conformance with the Principles is achieved;
• Secured independent assurance over the process to ensure stakeholder confidence and credibility in the process and conclusions; and
• Fully disclosed the status of OGC's conformance including instances of non-conformance and actions planned and undertaken to maintain conformance.

The Chief Sustainability Officer is responsible for overseeing the implementation and maintenance of conformance with the RGMPs. This role reports directly to the OceanaGold Chief Executive Officer and provides regular updates on Sustainability matters to the Board Sustainability Committee.

Reporting boundary

The boundary for implementing and reporting on the application of the RGMPs includes all mining and processing operations that OceanaGold has direct control over, as well the Group support offices. This is consistent with the reporting boundaries that OceanaGold publicly discloses in its annual Sustainability Report.

The OceanaGold operations included in the RGMP implementation and reporting boundary are:

• Haile Operation in the United States;
• Didipio Operation in the Philippines;
• Waihi Operation in New Zealand; and
• Macraes Operation in New Zealand.

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Description of key activities and achievements in 2023

In 2023, OceanaGold issued an externally-assuredRGMP 2022 Implementation Report confirming that the Company was in conformance with the RGMPs. The report also identified areas of work which OGC intended to undertake to further embed and underpin the implementation of the RGMPs.

Activities and achievements undertaken in 2023 to address these focus areas and to maintain conformance with the RGMPs included:

• Completed a review of third-party technology solutions to support a Modern Slavery risk assessment and due diligence of Tier 1 1 suppliers;
• Designed an enhanced ethical (modern slavery) risk methodology; and
• Configured the chosen technology solution to embed our risk methodology and automate workflow tasks. The enhanced methodology and technology solution was implemented across all sites on a pilot basis in 2023 and is continuing a phased roll-out in 2024.
• Human Rights training has been completed by all Executive Leadership Team members and all Senior Leadership team members are required to undertake the training. Conformance with this requirement is tracked by the Group Manager External
  Affairs and Social Performance and is reported in the annual Sustainability Report.
• All operations completed Human Right Impact Assessments (HRIAs) and social risk assessments and developed annual improvement plans based in these assessment findings.
• The OceanaGold Closure Standard has been reviewed against the ICMM framework and a work plan developed to align with the requirements of the ICMM framework.
• Commenced adoption of water accounting principles across OGC to drive greater consistency in water reporting and disclosures, and to facilitate development of group level water-related metrics across the Group.
• Energy and GHG emissions management plans were developed for each mine site in 2023 and monthly initiative tracking against plan, and reporting to management.
• An external review of our current risk management framework has been completed and findings presented to the Executive
  Leadership Team (ELT).
• ASupplier Code of Conduct was developed and approved by the CEO. The Code has been published on the OceanaGold website and has been directly communicated to our suppliers and contractors.
• During October 2023, an independent assessment of our conformance with the RGMPs was undertaken by BV in line with
  WGC assurance requirements. The assessment included a review of our governance requirements, policy commitments, performance standards and central processes as well as a detailed review of the RGMPs' application at Haile and more generally across all operations.

The findings of the 2023 assessment have been used to inform the content of this Conformance and Implementation Report. The 2023 assessment also identified specific areas for improvement and has been used to inform our 2024 Sustainability work plan.

Conformance status

At the time of the conformance assessment in October 2023, BV determined that OGC had demonstrated overall conformance with all Principles except Principle 3 - Supply Chain. An observation was also made regarding Principle 5 - Human Rights and Conflict. A summary of conformance findings is provided in the Table on page 5.

After this assessment, and as part of the 2023 planned Responsible Supply Chain work, the draft Supplier Code of Conduct was approved by the CEO and published to the OceanaGold website in English and in Tagalog (for Philippines stakeholders) in December 2023. The Code was also issued directly to our current suppliers and contractors.

In accordance with the requirements of the WGC's Conflict-Free Gold Standard OceanaGold has prepared a Conflict-Free Gold Statement for the 2023 year of operation. The Statement has been independently assured and supports OGC's conformance with RGMP Principle 5: Human Rights and Conflict.

1 Tier 1 suppliers relate to the direct suppliers we do business with.

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Based on the findings of the Bureau Veritas Assessment, the December 2023 launch of the Supplier Code of Conduct and the issuance of the OGC Conflict-Free Gold Statement, OGC confirms to the best of our knowledge, that the Company has demonstrated overall conformance with the requirements of the Responsible Gold Mining Principles in 2023.

This Statement of Conformance is provided by OceanaGold as part of the assurance requirements for the WGC's RGMPs, to meet the public disclosure requirements and to allow final independent assurance of OGC's conformance status to be issued.

Feedback with respect to this RGMP Implementation and Conformance Report, is welcome and may be provided to OceanaGold via [e-mail]

Independent assurance

OGC's 2023 RGMP Implementation and Conformance Report is subject to independent assurance. Bureau Veritas' Independent Assurance Report follows this Report as an Appendix.

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TABLE 1 - Summary of RGMP conformance assessment (October 2023)

Principle

Principle 1: ETHICAL CONDUCT

Principle 2: UNDERSTANDING OUR IMPACTS

Principle 3: SUPPLY CHAIN

Principle 4: SAFETY & HEALTH

Principle 5: HUMAN RIGHTS & CONFLICTS

Principle 6: LABOUR RIGHTS

Principle 7: WORKING with COMMUNITIES

Principle 8: ENVIRONMENTAL STEWARDSHIP

Principle 9: BIODIVERSITY, LAND USE and

MINE CLOSURE

Principle 10:

WATER, ENERGY and CLIMATE CHANGE

Findings and notes

OceanaGold has demonstrated overall conformance with the requirements of Principle 1 including sub-principles 1.1 to 1.7.

OceanaGold has demonstrated overall conformance with the requirements of Principle 2 encompassing subprinciples 2.1 to 2.5.

OceanaGold has demonstrated conformance with the requirements of sub- principles 3.2 and 3.3, however, a non-conformance with the requirements of sub-principle 3.1 was identified at the time of the assurance engagement

Non-conformance relating to the requirements of sub-principle 3.1:

At the time of the assurance engagement, the Supplier Code of Conduct was still in draft... In the absence of a dedicated Supplier Code of Conduct it could not be demonstrated that OceanaGold was monitoring suppliers/contractors' adherence to, and compliance with, its Code.

This non-conformance was addressed before the end of 2023. The Supplier Code of Conduct was published on our website soon after the assessment was completed in December 2023, bringing OceanaGold in conformance with this requirement by year-end.

OceanaGold has demonstrated overall conformance with the requirements of Principle 4 encompassing subprinciples 4.1 to 4.4.

OceanaGold has demonstrated overall conformance with the requirements of Principle 5 encompassing subprinciples 5.1 to 5.4.

Observation:

A follow-up with Didipio operations will be required to provide limited assurance on OceanaGold's Conflict-Free Gold Report (when completed).

Observation addressed. OceanaGold has prepared a Conflict-Free Gold Statement for the 2023 year of operation, in accordance with the requirements of the WGC's Conflict-Free Gold Standard. The OceanaGold Conflict-Free Gold Statement has been independently assured by BV. BV's Independent Assurance Report follows this Report as an Appendix.

OceanaGold has demonstrated overall conformance with the requirements of Principle 6 encompassing subprinciples 6.1 to 6.7.

OceanaGold has demonstrated overall conformance with the requirements of Principle 7 encompassing subprinciples 7.1 to 7.8.

OceanaGold has demonstrated overall conformance with the requirements of Principle 8 encompassing subprinciples 8.1 to 8.5.

OceanaGold has demonstrated overall conformance with the requirements of Principle 9 encompassing subprinciples 9.1 to 9.4.

OceanaGold has demonstrated overall conformance with the requirements of Principle 10 encompassing subprinciples 10.1 to 10.4

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Responsible Gold Mining Principles (RGMP)

Independent Assurance Report

To: The Directors of OceanaGold Corporation

Introduction and Objectives of Work

Bureau Veritas Australia Pty Ltd ("Bureau Veritas") was engaged by OceanaGold Corporation ("OceanaGold") to undertake a limited assurance engagement on the conformance with the Responsible Gold Mining Principles ("the Principles") for the year ended 2023. This Assurance Report applies to the related information included within the scope of assurance described below and presented in the OceanaGold Corporation - 2023 Responsible Gold Mining Principles Implementation and Conformance Report ("the Report").

Scope of Limited Assurance

The assurance scope consists of a review of the disclosures made by OceanaGold within the Report and the underlying systems, processes and performance to conform with the requirements of the Principles in place at its four operating assets: Haile Gold Mine (USA), Didipio Mine (Philippines), Waihi Operation (New Zealand) and Macraes Operation (New Zealand).

The Report was prepared following the illustrative criteria ("the Criteria") set out in the Guidance on Implementing and assuring the RGMPs: Supplement to the Assurance Framework issued by the World Gold Council.

Limited Assurance Conclusion

On the basis of our procedures as described under "Methodology" and the evidence we have obtained, we provide limited assurance that nothing has come to our attention to indicate that OceanaGold's conformance with the Principles as described in the Report is not fairly stated in all material respects. This conclusion is to be read in the context of the remainder of our report.

OceanaGold's Responsibilities

Management of OceanaGold is responsible for:

• Designing, implementing, operating and monitoring activities, processes and controls to ensure compliance with policies and procedures that conform with the Principles;
• Preparing and presenting the Report and information subject to our limited assurance in accordance with the Criteria; and
• Designing, implementing and maintaining internal controls over information relevant to the preparation of the Report that is free from material misstatement, whether due to fraud or error.

Our Responsibilities

Bureau Veritas is responsible for:

• Planning and performing the engagement to obtain limited assurance about whether the information included within the scope of assurance is free from material misstatement, whether due to fraud or error;
• Forming an independent conclusion, based on the procedures we have performed and the evidence we have obtained; and
• Reporting our conclusion to the Directors of OceanaGold.

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Responsible Gold Mining Principles (RGMP)

Independent Assurance Report

Methodology

Our limited assurance engagement was performed in accordance with International Standard on Assurance Engagements (ISAE) 3000 (Revised) Assurance Engagements other than Audits or Reviews of Historical Financial Information, issued by the International Auditing and Assurance Standards Board and the guidance set out in the Assurance Framework for the Responsible Gold Mining Principles and the Guidance on Implementing and assuring the RGMPs: Supplement to the Assurance Framework issued by the World Gold Council.

The extent of evidence-gathering procedures performed in a limited assurance engagement is less than for a reasonable level of assurance, and therefore a lower level of assurance is provided.

Our work was planned and executed in a manner designed to produce a limited level of assurance and to provide a sound basis for our conclusions. We undertook the following activities:

• Enquiries of management to gain an understanding of OceanaGold's processes and risk management protocols in place;
• Enquiries of staff responsible for the performance of the processes at corporate level and at selected sites, and for preparation of the disclosure related to the Principles;
• Visit to Corporate Head Office in Brisbane, Australia and to Haile Gold Mine in the USA which was selected taking account of the risk profile of the site;
• Review of documentary evidence produced by OceanaGold representatives;
• Audit of performance data and factual information including source verification;
• Interviews and follow-up communication with relevant individuals;
• Review of OceanaGold's processes for identification, aggregation and analysis of relevant information, report content and performance data; and
• Assessment of the suitability of policies, procedures and internal controls that OceanaGold has in place to conform with the Principles.

Inherent Limitations and Exclusions

Non-financial information, such as the OceanaGold's conformance with the Principles, is subject to more inherent limitations than financial information, given the more qualitative characteristics of the subject matter and the methods used for determining conformance. The absence of a significant body of established practice on which to draw to evaluate and measure non-financial information allows for different, but acceptable, measurement techniques and can affect comparability between entities and over time.

Excluded from the scope of our work is any assurance of information relating to:

• Statements of commitment to, or intention to undertake future actions by OceanaGold;
• Statements of position, opinion, belief and/or aspiration by OceanaGold;
• Financial data audited by an external third party; and
• Other sites and/or activities not included in the scope.

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Responsible Gold Mining Principles (RGMP)

Independent Assurance Report

Statement of Independence, Impartiality and Competence

Bureau Veritas is a global leader in Testing, Inspection and Certification ("TIC") services. The Group's mission is to reduce its clients' risks, improve their performance and help them innovate to meet the challenges of quality, health, safety, hygiene, environmental protection and social responsibility. Leveraging its renowned expertise, as well as its impartiality, integrity and independence, Bureau Veritas has helped build trust between companies, public authorities and consumers for more than 195 years.

Bureau Veritas has implemented a Code of Ethics across the business to maintain high ethical standards among its personnel in their day to day business activities. We are particularly vigilant in the prevention of conflicts of interest.

No member of the assurance team has a business relationship with OceanaGold, its Directors or Managers beyond that required of this assignment. We have conducted this assurance engagement independently and there has been no conflict of interest.

The assurance team was selected based on its extensive Industry Sector knowledge and experience in conducting independent verification, validation and assurance of Environmental Social and Governance (ESG) information and associated systems and processes.

We confirm that we satisfy the criteria for assurance providers as set out in the Assurance Framework for the Responsible Gold Mining Principles and the Guidance on implementing and assuring the RGMPs: supplement to the Assurance Framework issued by the World Gold Council.

Jeremy Leu

General Manager - Certification & Sustainability

17th April 2024

Bureau Veritas Australia Pty Ltd

ABN 15 090 874 570

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OceanaGold Corporation

Canada

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Vancouver, BC

V6C 3A6

[phone]

Australia

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[phone]

For further information: [e-mail]

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