IRM Investor Presentation

Q3 2023 RECONCILIATION OF REPORTED EPS TO ADJUSTED EPS Q3 2023 Q3 2022 Reported EPS - Fully Diluted from Net Income (Loss) Attributable to Iron Mountain Incorporated $0.31 $0.66 Add / (Deduct): Acquisition and Integration Costs 0.03 0.02 Restructuring and Other Transformation 0.13 0.01 (Gain) Loss on Disposal/Write-Down of PP&E, Net (0.02) (0.05) Other (Income) Expense, Net, Excluding our Share of Losses (Gains) from our Unconsolidated Joint Ventures Stock-Based Compensation Expense (0.06) (0.19) 0.06 0.05 Non-Cash amortization related to derivative instruments 0.02 Tax Impact of Reconciling Items and Discrete Tax Items (1) (0.03) (0.01) Adjusted EPS - Fully Diluted from Net Income (Loss) Attributable to Iron Mountain Incorporated $0.45 $0.48 IRON MOUNTAINⓇ (1) The difference between our effective tax rates and our structural tax rate (or adjusted effective tax rates) for the three months ended September 30, 2023 and 2022 is primarily due to (i) the reconciling items above, which impact our reported net income (loss) before provision (benefit) for income taxes but have an insignificant impact on our reported provision (benefit) for income taxes and (ii) other discrete tax items. Our structural tax rate for purposes of the calculation of Adjusted EPS for the quarters and year to date ended September 30, 2023 and 2022 was 13.3% and 16.5%, respectively. The Tax Impact of Reconciling Items and Discrete Tax Items is calculated using the current quarter's estimate of the annual structural tax rate. This may result in the current period adjustment plus prior reported quarterly adjustments not summing to the year to date adjustment. IRM INVESTOR PRESENTATION 28

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