Iron Mountain said it is filing Exhibit 99.1 describing the material U.S. federal income tax considerations related to the company's qualification and taxation as a real estate investment trust and the acquisition, ownership and disposition of its stock.

8-KOther EventsFiled Mar 9, 2026Period of report Mar 9, 2026Summary published (UTC) Oct 2, 2026

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Iron Mountain said it is filing Exhibit 99.1 describing the material U.S. federal income tax considerations related to the company's qualification and taxation as a real estate investment trust and the acquisition, ownership and disposition of its stock.
The company said the description in Exhibit 99.1 replaces prior descriptions of the federal income tax treatment of the company and its stockholders to the extent they are not consistent with the description in this Form 8-K.
The company listed an opinion from Sullivan & Worcester LLP on tax matters (Exhibit 8.1) and a consent (Exhibit 23.1) in its exhibit list, and said the consent is contained in Exhibit 8.1.
The company filed this Form 8-K under Item 8.01 (Other Events) on March 9, 2026, and it was signed by Michelle Altamura, Executive Vice President, General Counsel and Secretary.

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Analysis scope · Filing body only (exhibits excluded)We analyzed the filing body only. The exhibits exceeded the length limit and were excluded, so figures, financial statements and presentation materials in them were not reviewed.

Filing of Federal Income Tax Considerations Description

Iron Mountain said it is filing Exhibit 99.1 describing the material U.S. federal income tax considerations related to the company's qualification and taxation as a real estate investment trust and the acquisition, ownership and disposition of its stock.

Source · Based on the filing body (exhibits excluded)

Effect on Prior Tax Descriptions

The company said the description in Exhibit 99.1 replaces prior descriptions of the federal income tax treatment of the company and its stockholders to the extent they are not consistent with the description in this Form 8-K.

Source · Based on the filing body (exhibits excluded)

Tax Opinion and Consent Attached

The company listed an opinion from Sullivan & Worcester LLP on tax matters (Exhibit 8.1) and a consent (Exhibit 23.1) in its exhibit list, and said the consent is contained in Exhibit 8.1.

Source · Based on the filing body (exhibits excluded)

Filing and Signature Under Item 8.01

The company filed this Form 8-K under Item 8.01 (Other Events) on March 9, 2026, and it was signed by Michelle Altamura, Executive Vice President, General Counsel and Secretary.

Source · Based on the filing body (exhibits excluded)

AI summarized the filing and translated the summary into English; it may differ from the original. For reference only, not investment advice. AI translated the published Korean report into English. Figures are copied as filed, not recalculated.

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