October 1, 2025 – RSM Shiodome Partners Tax Co. and RSM Japan Tax Co. today announced the successful completion of their merger, effective October 1, 2025.

This merger brings together two highly regarded tax and accounting firms with deep expertise in serving public companies, pre-IPO firms, subsidiaries, and foreign-owned businesses. By joining forces, the firms will significantly expand their ability to support clients with cross-border transactions and global tax needs, while continuing to deliver high-quality, one-stop solutions.

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1. Why This Merger Matters

The integration enhances RSM’s presence in Japan and strengthens its role as a trusted advisor for businesses navigating international tax challenges. Clients will benefit from:

  • Broader expertise in international and domestic tax services
  • Greater resources for complex, cross-border transactions
  • A unified team of 250 professionals dedicated to supporting global growth

2. Post-Merger Structure

  • Firm Name: RSM Shiodome Partners Tax Co.
  • Head Office: Shiodome City Center 33F, 1-5-2 Higashi-Shinbashi, Minato-ku, Tokyo 105-7133
  • Branch Office: Shinjuku Island Tower 43F, 6-5-1 Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-1343
  • Website: https://shiodome.co.jp/spz/

3. About the Firms

RSM Shiodome Partners Tax Co.

  • Founded: 2012 (origins dating back to 2007)
  • Representative: Kengo Maekawa
  • Member of RSM International since 2022
  • Provides comprehensive tax and accounting services across multiple industries


RSM Japan Tax Co.

  • Founded: 2015 (with a history of international tax practice for over 25 years)
  • Representative: Akinaga Murayama
  • Specialized in serving foreign-owned companies and supporting cross-border business expansion
  • Merged with RSM Shiodome Partners Tax Co. in 2025

4. Looking Ahead

With this merger, RSM in Japan will build on its strong international network and proven expertise to deliver even greater value to clients. The firm remains committed to supporting businesses in an increasingly complex global environment and to raising the profile of the RSM brand in Japan.

5. Media Contact

RSM Shiodome Partners
Email: inquiry-jp [at] rsmjapan.com (please replace [at] with @)