Mercer Advisors Acquires AI Tax Firm Fifteenth to Expand Equity Compensation Expertise

Fifteenth gives Mercer Advisors a way to expand tax capacity through technology as well as staffing. The Denver-based wealth management firm has acquired the AI-native tax and accounting company, whose software is designed for equity compensation and complex tax situations. Mercer reported $114 billion in client assets as of September 30, 2026.

Announced November 5, 2026, the deal differs from Mercer’s earlier tax-focused acquisitions, which brought established accounting practices into the firm. Fifteenth combines a CPA team with a technology platform built to handle stock option exercises, tender offers, liquidity events and multi-entity filings. Its clients are largely technology company employees facing tax questions tied to equity compensation.

The acquisition also brings Fifteenth’s technology builders into Mercer. That matters because the firm is pursuing a model in which tax software supports professional teams and can extend their capacity. Mercer says Fifteenth’s platform can process complex returns faster and at greater scale than a model based solely on hiring more people.

Tax planning beyond filing season

Mercer says more than half of the ultra-high-net-worth clients who join the firm are seeking tax capabilities within a unified wealth management service. The company links that demand to increasingly complex wealth and a growing number of executive equity and liquidity events at growth-stage companies.

Tax professionals account for approximately one in 10 of Mercer’s roughly 1,880 employees. The firm expects that share to reach one in eight by the end of 2026. Fifteenth’s approach pairs planning throughout the year with annual tax preparation, positioning the work as an ongoing part of client service rather than a seasonal task.

Fifteenth serves more than 1,000 professionals. Its co-founders, Ankur Dahiya and Laura Moreno, will join Mercer as part of the transaction. Moreno, Fifteenth’s chief tax officer, said the company was built to make complex tax situations feel manageable for clients and that the deal creates an opportunity to serve more people.

Mercer Chief Platform Officer Cynthia Loh said Fifteenth’s AI tools have been refined through work supporting thousands of returns. Her point is central to the deal’s appeal: Mercer is adding technology that has already been used in tax workflows, alongside the people who built and operate it.

A different kind of acquisition

Mercer has been expanding its tax and accounting capabilities through purchases including Southern California firm Beach Freeman Lim & Cleland and Glass Jacobson, which added tax and accounting expertise. Those transactions expanded the firm’s pool of professionals. Fifteenth adds infrastructure intended to help that expertise reach more clients.

That distinction is relevant to a firm with a long acquisition record. Mercer passed the 100-deal mark in its decade-long acquisition strategy in May 2025. A technology platform that can be reused across client work offers a different path to growth than adding capacity only through additional hires, though its value will depend on how well it fits Mercer’s existing processes and serves clients at scale.

President Daniel Gourvitch described the firm’s partnership strategy as an effort to improve client experience, with technology working alongside experienced professionals. Fifteenth’s tax focus, he said, fits that model. The firm’s wider technology work points in the same direction: Mercer introduced the second generation of its AI-enabled Aspen platform in summer 2026 for its wealth advisory teams.

Connecting tax and private investments

The Fifteenth deal arrived amid other technology moves. On November 3, 2026, private markets infrastructure provider Arch announced a multi-year partnership with Mercer. Since work began in early 2025, Mercer says the system has saved more than 7,000 hours a year and cut the operating cost of managing client alternative investments by 40%. Those figures are as of August 31, 2026.

Arch automates the collection and routing of private investment information, including K-1s, capital calls, distributions and portfolio company updates, into Mercer’s advisory and reporting systems. Chief Investment Officer Don Calcagni said the platform gives advisors and clients visibility into private holdings similar to what they already have for public market investments.

Mercer says Arch connects with Aspen Investing. Alongside the Aspen advisory platform and Fifteenth’s tax tools, that points toward an operating setup in which private investment data, tax planning and financial planning can work through connected systems. The practical test will be whether that integration gives advisors useful information at the moments clients need to make decisions.

Fifteenth could also bring Mercer into client relationships earlier in the process of building wealth. Planning around a company sale, initial public offering or another major liquidity event may begin before a client transfers or invests substantial assets. That timing is particularly relevant for technology professionals whose wealth may be concentrated in unvested shares and options, and who have often relied on standalone tax advisors or specialists in equity compensation.

Mercer operates through more than 120 locations and is majority-owned by Oak Hill Capital, Genstar Capital, Altas Partners and GIC. The firm was ranked the No. 1 RIA firm for the past three years in Barron’s Top 100 Registered Investment Advisor Firms rankings. Together, its recent moves show a push to build technology into tax and private investment operations as its services grow for complex client needs.