Complexity to clarity, wherever you are in the world
At Ostberg Sinclair & Co. we believe that great tax advice is only as valuable as the way it’s delivered.
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US Private Clients
Get help navigating complex compliance and planning opportunities in the US, UK and internationally.
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UK Private Clients
Effective advice and strategic tax management, ensuring you’re being as economical as possible while meeting compliance obligations.
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US Corporate & International Tax
Make sure you’re compliant with tax regulations, and get support for connected individuals, without ambiguity.
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Trusts, Estates, & Family Services
Get help with estate, inheritance, and divorce planning, and ensure tax compliance in line with your fiduciary obligations.
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US Connected Business Owners & Entrepreneurs
Helping you navigate the complex rules that apply to US connected people.
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Delinquent US Filers
Helping you seamlessly navigate your route to compliance whilst mitigating risk.
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UK Business Tax Advisory
Practical, commercial, and cross-border insight for entrepreneurs, investors and growing companies.
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Partnership & Fund Reporting
Corporate and partnership tax returns and bespoke structuring support to help you attract global investment.
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Employer Solutions
Providing support and solutions to help employers stay compliant, maximise tax efficiency, and reduce costs.
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Global Mobility Services
Taking the complexity out of moving employees and directors to and from the UK.
DR DRE“The only two things that scare me are God and the IRS”
Why Ostberg Sinclair & Co?
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.
Latest knowledge
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Are You Managing Payroll Risks Across Borders?
4th September 2026
Remote and internationally mobile working arrangements have become increasingly common. While these arrangements can provide greater flexibility for both employers and employees, they can also create complex payroll, tax, social security, and compliance obligations across multiple jurisdictions.
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IR35 and Off-Payroll Working: Understanding Your Risk Profile
28th August 2026
IR35 remains a significant tax risk for UK businesses, with common compliance issues around contractor status, company size, supply chains and overseas workers potentially leading to substantial PAYE and NIC liabilities.
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Short-Term Business Visitors to the UK: Don't Let a Two-Day Trip Create a Tax Problem
21st August 2026
When overseas employees visit the UK for meetings, training, client engagements, or project work, tax compliance is rarely front of mind. However, HMRC's rules are often far stricter than employers expect.
Ready to turn complexity into clarity?
We’re here to help you make informed decisions, with confidence.