7 Financial Mistakes American Expats Make When Moving to the UK

Moving across the Atlantic is a dream for many Americans. Historic cities, rolling countryside, cultural variety, and the chance to live and work in one of the world’s most international hubs are powerful attractions. But when the excitement of relocating to the UK meets the reality of financial planning, many expats quickly realize they have overlooked key details.

Those oversights often translate into unnecessary stress, double taxation, or thousands of dollars lost.

To help you prepare, here are 7 of the most common financial mistakes Americans make when relocating to the UK, along with practical ways to avoid them.

1. Ignoring Tax Obligations in Both Countries

One of the most common and costly assumptions expats make is believing that leaving the U.S. means leaving the IRS behind. Unfortunately, that is not how it works. The United States is one of the only countries in the world that taxes based on citizenship rather than residency. Even if you live in London for the next 30 years, you must still file an annual U.S. tax return.

On top of that, you will need to file in the UK once you are considered a tax resident there. The dual filing requirement does not always mean you will pay double tax, but it does create extra paperwork, deadlines, and complexity. Failing to file can trigger hefty penalties even if you do not owe any U.S. tax at the end of the day.

What to do instead: Recognize from the start that you are living in two tax systems at once. Work with a cross-border accountant who can help you meet both sets of requirements efficiently.

2. Overlooking the U.S.–UK Tax Treaty

The U.S. and the UK have a tax treaty designed to prevent double taxation. But it is not automatic. You need to actively claim treaty benefits, often by filling out extra IRS forms or adjusting your UK filings. Without doing so, you might pay unnecessary tax on income that is already covered under the treaty.

For example, certain types of retirement income, dividends, or business profits may be shielded by treaty provisions. Many expats do not realize this until they have already paid tax twice.

What to do instead: Learn which sections of the treaty apply to your situation, especially if you have income from investments, pensions, or rental property. A specialist tax advisor can ensure you claim the right reliefs and credits.

3. Mishandling Retirement Accounts

If you have savings in U.S. retirement accounts such as 401(k)s or IRAs, relocating complicates things. The U.S. may tax distributions in one way, while the UK may treat them differently. In some cases, contributions to UK pensions can also create U.S. reporting challenges.

Another pitfall is forgetting that retirement rules differ across borders. Required minimum distributions, contribution limits, and tax relief mechanisms do not align neatly between the two countries.

What to do instead: Before moving, create a retirement strategy that considers both U.S. and UK rules. Sometimes it makes sense to pause contributions, consolidate accounts, or rely on treaty provisions to avoid double taxation.

4. Holding the Wrong Investment Accounts

Many Americans assume their U.S. brokerage accounts will work the same way abroad. Unfortunately, the UK tax authority (HMRC) may classify certain U.S. investments, particularly mutual funds and ETFs, as Passive Foreign Investment Companies (PFICs).

PFICs are a compliance nightmare. They come with extremely complex IRS reporting rules and punitive tax treatment. An account that felt perfectly normal in the U.S. can become a liability once you are overseas.

What to do instead: Review your investment portfolio before relocating. In some cases, selling and restructuring investments before moving makes sense. Alternatives such as holding U.S.-listed individual stocks or working with a cross-border investment advisor can reduce your exposure to PFIC issues.

5. Currency Exchange at Retail Rates

Another mistake is underestimating the cost of moving money between dollars and pounds. Using your U.S. bank, swiping your American credit card, or transferring money through retail channels often comes with unfavorable exchange rates and hidden fees. Over time, those costs add up, especially if you are paying rent, tuition, or mortgage payments in pounds.

What to do instead: Shop around for specialist foreign exchange services or open a multi-currency account. Services like Wise, Revolut, or dedicated FX brokers often provide better rates and lower fees than traditional banks.

6. Not Updating Estate and Inheritance Planning

Cross-border inheritance planning is complex. The U.S. and UK both have estate or inheritance tax systems, but the thresholds, rates, and exemptions differ. Without proper planning, your heirs could be subject to taxation in both countries.

Additionally, wills drafted in the U.S. may not align with UK law. Something as simple as how property is titled or how trusts are structured could create unnecessary tax burdens.

What to do instead: Review your estate plan with an attorney who understands both systems. This ensures that wills, trusts, and beneficiary designations are valid and tax-efficient across borders.

7. Assuming Healthcare Costs Are Fully Covered

The UK’s National Health Service (NHS) is a point of pride and a significant financial benefit for residents. However, many expats arrive assuming it is completely free and covers every service. That is not the case.

Dental care, prescriptions, optical services, and certain treatments often carry charges. Waiting times for non-urgent procedures can also be long, leading many expats to purchase private health insurance in addition to NHS coverage. Ignoring these costs in your budget can leave you unprepared.

What to do instead: Research the NHS entitlements you will have as a resident and factor in potential costs for supplemental insurance, dental care, and prescriptions.

Relocating to the UK can be one of the most rewarding experiences of your life. But financial mistakes can quickly turn the excitement of your new adventure into frustration. From taxes to retirement, investments to estate planning, Maseco Private Wealth can help you understand the cross-border implications that will save you money and stress.

The key takeaway is simple. Do not assume that what worked in the U.S. will automatically transfer overseas. Seek advice from professionals who specialize in U.S.–UK cross-border finances, plan ahead, and give yourself a smoother start in your new home.