Combining multinational-level expertise with the agility and attention of a boutique firm
At Ostberg Sinclair & Co., we believe that great tax advice is only as valuable as the way it’s delivered. Our approach is to declutter complexity and turn difficult technical concepts into simple actionable steps while minimizing risk.
Every engagement begins with understanding – your goals, circumstances, and the details that matter most and which make each of our clients one of a kind. We then translate the intricacies into clear, practical steps, enabling you to make informed decisions with confidence.
With this we craft strategies that fit your priorities, whether that’s cross-border tax compliance, structuring for growth or safeguarding family wealth. We handle the detail, so you don’t have to – keeping you informed without overloading you.
Life changes, and so do tax rules. We stay close, adjusting plans as needed, providing proactive guidance when new opportunities or challenges arise.
Our story
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 and 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.
WARREN BUFFET“You only have to do a few things right in your life so long as you don’t do too many things wrong”
Ready to turn complexity into clarity?
We’re here to help you make informed decisions, with confidence.