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About Us

Welcome to Optimise Accountants, your trusted partner for international tax advice and support. Founded in 2003 by Simon Misiewicz, a UK-qualified accountant (ACCA), UK tax advisor (ATT), and American tax advisor (Enrolled Agent), we have been at the forefront of providing expert tax guidance to individuals and businesses navigating the complexities of cross-border taxation. With over a decade of specialised experience in international tax advice since 2013, we are uniquely positioned to help clients understand their tax obligations and opportunities wherever they are.

Our Core Services

We aim to be the best one-stop shop for Americans living in the United Kingdom or Spain with their tax filing with the Internal Revenue Service (IRS) and/or HMRC (UK) and/or Agencia Tributaria. This aim also applies to British citizens who have moved to the United States and/or Spain.

We are well-positioned to give expat tax guidance for those who invest or live in the US, UK and/or Spain. We are well-versed in the nuances of the tax treaties and how to apply them to your tax filings with the IRS, HMRC and Agencia Tributaria.

Our Mission

At Optimise Accountants, our mission is simple: to provide clear, effective, and personalised tax solutions for individuals and businesses facing the challenges of international relocation. Whether you’re an American moving abroad or a UK citizen seeking opportunities overseas, we are here to ensure your transition is as tax-efficient as possible. By understanding and utilising international tax treaties, we aim to help our clients minimise their tax liabilities and avoid costly mistakes.

Expertise in US Tax for Americans Abroad

For Americans moving to the UK, Spain, Canada, or any other country, our expertise ensures you remain compliant with US and foreign tax laws. As an American, even when living abroad, you are required to file a 1040 tax return to the Internal Revenue Service (IRS). Our team provides in-depth advice on managing your ongoing tax obligations, such as filing for foreign-earned income exclusions, claiming foreign tax credits, and understanding the complex rules around dual tax residency.

Beyond compliance, we also help Americans minimise their income tax, capital gains tax, and estate tax liabilities when moving to a new country. Understanding how your international income, investments, and assets are taxed in the US and your new home country is critical to avoiding double taxation. With the right guidance, we help our clients navigate tax complexities efficiently and effectively.

Supporting British Citizens Moving Abroad

We also provide specialised tax advice to British citizens moving to the US, Canada, Spain, or elsewhere. Many people don’t realise that even after leaving the UK, there may still be a requirement to file a UK self-assessment tax return with HMRC. This is particularly important if you have income-generating assets such as property, investments, or businesses operating in the UK.

Our team helps UK expatriates understand what to do with their homes, investments, and businesses when relocating. Moving money or selling assets after you’ve moved to a new country can have significant tax consequences. Without proper advice, there’s a real risk of paying tax twice. We are experts in interpreting Double Taxation Agreements (DTAs) and helping our clients make smart decisions to avoid this pitfall.

Optimise Accountants with Simon Misiewicz, your partner for UK, US and international tax advice and support when living abroad as an expat.

Comprehensive Advice on Investments, Homes, and Businesses

Relocating internationally is a significant financial decision, and the tax implications can be overwhelming. When moving countries, we aim to provide our clients with the best possible advice on managing their wealth, homes, investments, and businesses. Selling a home, cashing out investments, or moving business operations can trigger complex tax rules. We help our clients make informed decisions so they don’t fall into tax traps or face unexpected liabilities.

Linette Coe: A Trusted Partner

At Optimise Accountants, I am proud to be supported by Linette Coe, who shares the same qualifications as me, Simon Misiewicz. Linette is a UK-qualified accountant (ACCA), UK tax advisor (ATT), and an American tax advisor (Enrolled Agent), making her well-equipped to assist with both UK and US tax obligations.

Together, we provide tailored tax advice and filing services for Americans and British citizens who need to understand their dual tax responsibilities. Linette’s deep knowledge and commitment to delivering practical, personalised solutions have helped many of our clients confidently navigate their tax situations.

Why Choose Us?

At Optimise Accountants, moving to a new country involves more than just packing your bags—it’s about protecting your financial future. Here’s why clients trust us:

Specialised Knowledge: With over a decade of international tax experience, we understand the intricacies of cross-border tax laws.

Tailored Advice: We provide personalised advice based on your unique financial situation, ensuring you make the best decisions for your tax planning.

Dual Expertise: We are qualified to advise on UK and US tax laws, making us a one-stop solution for your international tax needs.

Whether you’re an American looking to move to the UK or a Brit setting up in the US, our advice can help save you from making costly mistakes. We are committed to ensuring our clients avoid double taxation, maximise tax benefits, and meet all filing obligations on time.

Get in Touch

If you’re planning an international move or have already relocated and need tax advice, Optimise Accountants is here to help. Contact us today to schedule a consultation, and let us guide you through the complexities of cross-border tax planning. With our expertise and personalised approach, we’ll help you make informed decisions, reduce your tax liabilities, and ensure full compliance with both US and UK tax laws.