Mercer Advisors, the Denver-based registered investment advisor with $114 billion in client assets, has acquired Fifteenth, an artificial intelligence-native tax and accounting firm whose proprietary platform is purpose-built for equity compensation and complex tax situations.
The deal was announced November 5, 2026, and marks a departure from Mercer's earlier tax-focused acquisitions, which centered on established CPA practices as Fifteenth is a technology company first.
Its AI platform was built specifically to handle stock option exercises, tender offers, liquidity events, and multi-entity filings for professionals at Silicon Valley technology firms. The acquisition brings both a CPA team and the firm's tech builders into Mercer Advisors, reinforcing what the firm describes as an ambition to become a destination employer for financial services technologists.
"What sets Fifteenth apart is that their AI capabilities aren't theoretical," said Cynthia Loh, Chief Platform Officer of Mercer Advisors. "They've been built and refined through supporting thousands of returns, real numbers that made us excited about bringing their time-tested technology into our organization."
The acquisition reflects a broader shift inside Mercer Advisors. More than half of the ultra-high-net-worth clients who join the firm are actively seeking tax capabilities as part of a unified wealth management offering - a trend the company attributes to rising wealth complexity and an accelerating wave of executive equity and liquidity events across growth-stage companies.
Tax professionals now make up approximately one in 10 of Mercer's roughly 1,880 employees, a ratio the firm expects to reach one in eight by the end of 2026, according to the company. AI tax-planning software has become the highest-impact AI category in RIA practices in 2026, making Fifteenth's model - which pairs year-round planning with annual preparation rather than treating tax as a filing-season service - particularly attractive to a firm competing at the top of the market.
Fifteenth currently serves more than 1,000 professionals, with its client base concentrated among employees of technology companies navigating equity-driven wealth events. Its co-founders, Ankur Dahiya and Laura Moreno, will join Mercer Advisors as part of the transaction.
"We built Fifteenth around a simple idea: even the most complex tax situations shouldn't have to feel complex for the client," said Laura Moreno, Chief Tax Officer and Co-Founder of Fifteenth. "Joining Mercer Advisors gives us the opportunity to bring that combination to more clients at greater scale."
The Fifteenth deal stands apart from the string of CPA and planning-focused acquisitions Mercer Advisors has completed in recent years.
These include Beach Freeman Lim & Cleland, a Southern California tax firm, in a move that marked Mercer's first addition of a tax-focused RIA, and Glass Jacobson, which added further tax and accounting specialties to the national RIA, which has been steadily expanding its expertise in those areas. Those deals added tax professionals; this one adds a technology infrastructure that can extend those professionals' capacity.
Fifteenth's platform can process complex returns faster and at greater scale than a purely headcount-driven model, Mercer said. That positions it differently from traditional tax acquisitions, where capacity gains track directly to hiring. For a firm that surpassed the 100-deal milestone in its decade-long acquisition strategy in May 2025, adding repeatable technology rather than personnel is a meaningful evolution.
"Our partnership strategy is ultimately about building a better experience for clients, and technology that works in partnership with high-caliber professionals is a significant part of that," said Daniel Gourvitch, President of Mercer Advisors. "Fifteenth fits that model with a tax focus and technology that can be extended to the clients who need it."
The firm's investment in AI extends beyond this deal. In the summer of 2026, Mercer unveiled the second generation of Aspen, its AI-enabled platform used by its wealth advisory teams, a signal that artificial intelligence is becoming infrastructure at the firm, not just a feature.
For Mercer Advisors, Fifteenth also creates a channel into client relationships earlier in the wealth creation cycle. By supporting clients ahead of a sale, initial public offering, or other major liquidity event - not just at filing time - the firm can establish a planning relationship before significant assets are transferred or invested.
That upstream engagement has become a differentiator in the competition for high-net-worth clients, particularly among technology professionals whose wealth is concentrated in unvested stock and options.
Financial advisors watching the mega-RIA landscape will recognize this as a deliberate move to deepen relevance with a client segment that has historically turned to standalone tax advisors or boutique equity compensation specialists for complex situations.
The Fifteenth deal is the latest in a rapid series of technology moves at Mercer Advisors.
On November 3, 2026, Arch, the infrastructure layer for private markets, announced a multi-year partnership with Mercer Advisors powering scale in private markets management while reducing operational risk. Since their work began in early 2025, Mercer Advisors has saved more than 7,000 hours a year, reducing the operational cost of managing client alternative investments by 40%.
The Arch platform automates the collection and routing of private markets data - K-1s, capital calls, distributions, and portfolio company updates - feeding information into Mercer’s central advisory and reporting systems.
“Arch has become a key component of our private investments platform and operations, bringing critical investment data into our central advisory platform and giving advisors and clients real-time visibility into private investments, much like they already have with public markets,” said Don Calcagni, Chief Investment Officer at Mercer Advisors.
Taken together, the two announcements signal that Mercer Advisors is building AI into its operational layer - not deploying point solutions. Tax complexity and alternatives complexity are both being addressed through technology designed to scale with the firm’s growing roster of ultra-high-net-worth client families.
Mercer unveiled the second generation of its Aspen AI-enabled advisory platform in the summer of 2026, and the Arch integration connects directly to Aspen Investing - meaning private markets data, tax planning, and financial planning are increasingly flowing through a single connected infrastructure.
Mercer Advisors is majority-owned by Oak Hill Capital, Genstar Capital, Altas Partners, and GIC. The firm operates nationally through more than 120 locations and was ranked the No. 1 RIA firm for the past three years by Barron’s Top 100 Registered Investment Advisor Firms rankings. Company statistics for the Fifteenth announcement are as of September 30, 2026; Arch partnership statistics are as of August 31, 2026.
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