Ostberg Sinclair & Co., was founded with a clear purpose: to put people first. After years of leading successful teams at Big Four and top-tier firms, our leadership saw an opportunity to create something different—a boutique advisory practice built around relationships, not rigid processes.

From the outset, we’ve challenged convention. We believe clients deserve not only technical excellence but empathy, clarity, understanding that culminates in advice tailored to their unique circumstances. That’s why we’ve built a conflict-free environment where complex tax, succession, and structuring issues are handled with care.

Our ethos is simple: every client is a person, not a case file. This values-driven approach has earned us recognition, including Tolley’s Taxation Award for Best New Practice in 2025. But accolades aside, what matters most is trust – the trust our clients place in us to navigate the complexities of international tax and private client services.

Today, Ostberg Sinclair & Co. offers a full suite of services for US and UK private clients, entrepreneurs, and businesses with cross-border interests. Our team combines multinational-level expertise with the agility and attentiveness of a boutique firm, delivering solutions that are strategic, practical, and tailored to you.

Measured growth. High-quality work. Relationships that stand the test of time. That’s our story – and we’re just getting started.

Ostberg Sinclair & Co

Aldwych House serves as a hub for tax consultancy and business advisory services, focusing on private clients and international tax.

Aldwych House

Jillian Symes

This department focuses on managing and advising on tax compliance, planning, and analysis.

Tax Services

This department oversees tax planning, compliance, and advisory services for various jurisdictions.

Tax Management

This department focuses on developing and maintaining strategic partnerships to drive business growth and collaboration.

Partnership Management

This department assists senior management with administrative tasks and operational support to enhance productivity.

Management Support

This department provides essential administrative assistance to ensure smooth operations and effective communication across the organization.

Administrative Support

This department oversees strategic direction and decision-making processes within the organization.

Ostberg Sinclair & Co

Org chart

Teams

Tax Services

Tax Management

Partnership Management

Management Support

Administrative Support

Leadership Coordination

Offices

Ostberg Sinclair & Co

Org chart

Teams

Tax Services

Tax Management

Partnership Management

Management Support

Administrative Support

Leadership Coordination

Offices

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