Mercer Advisors acquires AI-native tax and accounting firm Fifteenth

By Amara Osei

Mercer Advisors acquired AI-native tax and accounting firm Fifteenth, adding specialized tax and AI capabilities to a wealth platform overseeing approximately $114 billion in client assets.

According to Mercer Advisors’ announcement, the deal adds specialized tax expertise and AI engineering talent to Mercer’s tax operations. It extends the firm’s investment in AI-enabled software into tax planning and accounting.

What does Fifteenth add to Mercer’s tax business?

Fifteenth combines experienced tax professionals with an AI platform designed for clients facing complex financial circumstances. The company provides annual tax preparation and ongoing planning, and its customer base includes professionals at Silicon Valley technology companies.

Fifteenth’s service mix covers four areas:

• Stock option exercises
• Tender offers
• Corporate liquidity events
• Tax filings involving multiple entities

More than 1,000 professionals currently use Fifteenth’s technology and services, according to Mercer Advisors. Fifteenth designed the platform to help tax professionals analyze tax requirements and prepare filings involving sophisticated financial arrangements.

Ankur Dahiya, CEO and co-founder of Fifteenth, said:

“Fifteenth combines personalized, high-touch service with the power of modern software, and we are excited to bring our specialized tools that are already serving more than 1,000 professionals to more families through our partnership with Mercer Advisors.”

How will Mercer’s tax workforce change?

Mercer intends to integrate Fifteenth’s platform with its existing tax operations to increase professional-team capacity. The company believes automation can help advisors handle more complex assignments while preserving personalized service.

Tax specialists currently account for approximately one in 10 employees. Mercer expects that ratio to reach one in eight by the end of 2026. Fifteenth’s automation and workflow tools could support the expansion.

Cynthia Loh, Chief Platform Officer of Mercer Advisors, said:

“What sets Fifteenth apart is that their AI capabilities aren’t theoretical. 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.

As we integrate their tools alongside our existing tax infrastructure, we expect to meaningfully expand the capacity of our tax teams while continuing to deliver the high level of expertise and service our clients expect.

Just as important, Fifteenth’s team joins a firm where talented technologists can build practical AI that makes a real difference for clients. We want Mercer Advisors to be the home for great tech talent that wants to do meaningful work.”

Why does Mercer want deeper tax capabilities?

The acquisition supports Mercer’s broader strategy to provide comprehensive wealth management and family office services. Mercer Advisors’ offering spans six areas:

• Financial planning
• Investment management
• Tax planning and preparation
• Estate planning
• Insurance solutions
• Trust-related services

For high-net-worth clients, tax decisions frequently intersect with investment strategies, business ownership, equity compensation, and wealth transfers. Mercer believes the integration can improve financial planning outcomes and simplify clients’ experience.

According to the company, more than half of incoming ultra-high-net-worth clients seek tax capabilities within a broader financial advisory relationship. The company also links demand to increasingly complex personal finances and liquidity events involving executives and business owners. Fifteenth’s stock-based compensation experience gives Mercer additional resources for those situations.

Laura Moreno, Chief Tax Officer and co-founder of Fifteenth, said:

“We built Fifteenth around a simple idea: even the most complex tax situations shouldn’t have to feel complex for the client. Technology is a huge part of how we deliver on that promise, but so is the judgment of experienced tax professionals.

Joining Mercer Advisors gives us the opportunity to bring that combination to more clients at greater scale. And for our existing clients, it means the tax experience they know can now connect to comprehensive wealth management, giving them a deeper context for Economic Freedom.”

Where does the AI strategy go next?

Mercer Advisors has invested in AI-enabled software across its wealth management business. During summer 2026, the company introduced the second generation of Aspen, an AI-powered platform supporting advisory teams.

Fifteenth extends that technology strategy into tax planning and accounting through its proprietary AI platform. Fifteenth Co-Founder and CEO Ankur Dahiya and Co-Founder and Chief Tax Officer Laura Moreno are joining Mercer, which intends to support continued development of the acquired technology.

Mercer Advisors employs more than 1,880 people and operates from more than 120 locations nationwide. Oak Hill Capital, Genstar Capital, Altas Partners, and GIC majority-own the firm, according to the announcement.

Mercer Advisors’ approximately $114 billion in client assets comprises assets under management, assets under advisement, and certain assets associated with recent acquisitions. The company said the acquisition strengthens its ability to coordinate tax services with broader wealth management activities.

Daniel Gourvitch, President of Mercer Advisors, said:

“We are excited to welcome Fifteenth’s team to the partnership. They created Fifteenth to combine sophisticated tax support with AI-driven solutions for tax professionals.

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. Fifteenth fits that model with a tax focus and technology that can be extended to the clients who need it.”

Mercer’s stated near-term goal is to use Fifteenth’s automation to expand tax-team capacity while its specialist ratio reaches one in eight by the end of 2026. The acquisition gives the firm a broader platform for connecting tax decisions with investments, business ownership, equity compensation, and wealth transfers.