Report of Independent Accountants

To the Board of Directors of Mercer International Inc.

We have reviewed the select performance metrics included in the accompanying Appendix I (the subject matter) within Mercer International Inc.’s 2024 Sustainability Report, as of and for the year ended December 31, 2024. Mercer International Inc.’s management is responsible for the subject matter in accordance with the criteria included in Appendix I. Our responsibility is to express a conclusion on the subject matter based on our review.

Our review was conducted in accordance with attestation standards established by the American Institute of Certified Public Accountants (AICPA) in AT-C section 105, Concepts Common to All Attestation Engagements, and AT-C section 210, Review Engagements, and standards established by the International Auditing and Assurance Standards Board (IAASB) in International Standard on Assurance Engagements (ISAE) 3000, Assurance Engagements Other than Audits or Reviews of Historical Financial Information, and International Standard on Assurance Engagements (ISAE) 3410, Assurance Engagements on Greenhouse Gas Statements. Those standards require that we plan and perform the review to obtain limited assurance about whether any material modifications should be made to the subject matter in order for it to be in accordance with the criteria. The procedures performed in a review vary in nature and timing from, and are substantially less in extent than, an examination, the objective of which is to obtain reasonable assurance about whether the subject matter is in accordance with the criteria, in all material respects, in order to express an opinion. Accordingly, we do not express such an opinion. Because of the limited nature of the engagement, the level of assurance obtained in a review is substantially lower than the assurance that would have been obtained had an examination been performed. We believe that the review evidence obtained is sufficient and appropriate to provide a reasonable basis for our conclusion.

We have complied with the independence and other ethical requirements of the International Code of Ethics for Professional Accountants (including International Independence Standards) issued by the International Ethics Standard Board for Accountants (IESBA Code) and of the relevant rules of professional conduct / code of ethics applicable to the practice of public accounting and related to assurance engagements, issued by various professional accounting bodies, which are founded on fundamental principles of integrity, objectivity, professional competence and due care, confidentiality and professional behaviour.

The firm applies Canadian Standard on Quality Management 1, Quality Management for Firms that Perform Audits or Reviews of Financial Statements, or Other Assurance or Related Services Engagements, which requires the firm to design, implement and operate a system of quality management including policies or procedures regarding compliance with ethical requirements, professional standards and applicable legal and regulatory requirements.

The procedures we performed were based on our professional judgment. In performing our review, we performed analytical procedures, inquired of persons responsible for the subject matter, read relevant policies to understand terms related to the select performance metrics, reviewed supporting documentation in regard to the completeness and accuracy of the data on a sample basis, and obtained an understanding of the data management systems and processes used to generate, aggregate, and report the subject matter.

Greenhouse gas (GHG) emissions quantification is subject to significant inherent measurement uncertainty because of such things as GHG emissions factors that are used in mathematical models to calculate GHG emissions, and the inability of these models, due to incomplete scientific knowledge and other factors, to accurately measure under all circumstances the relationship between various inputs and the resultant GHG emissions. Environmental and energy use data used in GHG emissions calculations are subject to inherent limitations, given the nature and the methods used for measuring such data. The selection by management of different but acceptable measurement techniques could have resulted in materially different amounts or metrics being reported.

The preparation of the subject matter requires management to establish the criteria, make determinations as to the relevancy of information to be included, and make assumptions that affect reported information. The selection by management of different but acceptable measurement techniques could have resulted in materially different amounts or metrics being reported.

As discussed in the “Key Methodologies” Appendix of Mercer’s 2024 Sustainability Report, in 2023, Mercer International Inc. applied a different measurement method for Greenhouse Gas Emissions Scope 2 (Location based), Net energy consumption and Gross energy consumption from renewable sources.

Based on our review, we are not aware of any material modifications that should be made to the subject matter, included in Mercer International Inc.’s 2024 Sustainability Report, as of and for the year ended December 31, 2024, in order for it to be in accordance with the criteria described in the Appendix I.

Our report has been prepared solely for the Board of Directors of Mercer International Inc. for the purpose of assisting management in reporting to the directors on its select performance metrics. The subject matter therefore may not be suitable, and is not to be used, for any other purpose. Our report is intended solely for Mercer International Inc.

We neither assume nor accept any responsibility or liability to any third party in respect of this report.

PricewaterhouseCoopers LLP

Chartered Professional Accountants
Vancouver, BC, Canada
May 27, 2025