Tax expert says this one mistake costs expats thousands each year: Here’s how to avoid it

How a single oversight before your move abroad can drain your savings, and the simple step to avoid it, writes Expat Tax Thailand, www.expattaxthailand.com.

Key points:

• Expat tax expert reveals the costly mistake thousands make before moving abroad, and it's easier to avoid than you think
• Expert explains why timing your move by just a few weeks can mean the difference between keeping your money and losing thousands
• Tax specialist shares essential steps to protect your finances before relocating overseas

More people than ever are packing their bags and heading abroad. Whether it's for work, retirement, or a fresh start, expat life has never been more appealing. The freedom, the adventure, the chance to reinvent yourself in a new country… it's no wonder millions are taking the leap.

But here's the problem: every year, countless expats watch thousands slip through their fingers. Not because of bad luck or poor financial decisions, but because of one simple oversight before they even board the plane.

The mistake? Moving abroad without proper tax planning.

“People focus on visas, housing, and learning the local language,” explains Carl Turner, co-founder of Expat Tax Thailand, a tax advisory service helping expats understand their obligations in Thailand. “But they completely overlook how their move date, asset transfers, and financial setup will affect their tax bill. By the time they realize, it's too late to fix.”

Below, Carl reveals why this oversight is so costly, and what you need to do before you move to protect your money.

Why moving without professional tax planning is so costly

When most people plan an international move, they think about practicalities: finding a place to live, shipping belongings, sorting out visas. Tax planning rarely makes the list. But this oversight can be expensive.

“I've seen people lose hundreds of thousands of dollars simply because they moved two weeks earlier than they should have or didn’t sell certain assets before they moved which would have saved them money due to differing tax rules,” says Carl. “Or they sold property at the wrong time. These are timing issues that proper planning would have caught.”

The problem is that tax rules don’t line up neatly across borders. Each country has its own tax year, residency rules, exemptions, and special treatment for things like a main residence, pensions, and tax-favoured investments. An asset that is completely tax-free in one country may become fully taxable the moment you become resident somewhere else.

Time your move badly, and you could find yourself paying tax in your new country on the sale of assets that would have been exempt if sold before leaving. Likewise, disposing of or transferring investments after you arrive may trigger capital gains tax simply because your new country doesn’t recognise the same reliefs you enjoyed at home.

While true “double taxation” is usually avoided when a Double Taxation Agreement (DTA) exists, it can still occur if there is no treaty in place, or if the two countries classify the income differently or apply reliefs in conflicting ways. In other words, the timing of your move can determine whether a transaction is tax-efficient, or unexpectedly expensive.

Common consequences of poor planning

The financial impact of moving without tax planning amounts to more than only paying additional tax. Carl explains what can happen:

• Double Taxation: You might end up paying tax on the same income in both countries. While tax treaties exist to prevent this, claiming relief requires paperwork, time, and often professional help, all costs that add up quickly.
• Losing Tax-Free Allowances: Expats often don't realise they have capital gains allowances, dividend allowances, and personal savings allowances in their home country. Use them strategically before you move, and you can shield significant income from tax. Waste them, and you're paying tax you didn't need to.
• Unexpected Tax Residency: Some countries have different rules about when you become a tax resident. You might think you're not a Thai tax resident yet because you've only been there a few months, but if you've spent more than 180 days in the tax year, you are for the whole calendar year. That changes everything about what income gets taxed and where.
• Pension Problems: Moving abroad can affect your pension in ways you don't expect. Some countries even tax UK pension commencement lump sums (PCLS); others don’t. Getting advice before you move means you can structure things properly from the start.
• Tax-Efficient Wrappers Aren’t Always Tax-Free Abroad: Many UK expats assume ISAs, LISAs, and other tax-efficient accounts stay tax-free when they move overseas. They don’t. Once you become tax resident elsewhere, the new country can tax the income and gains inside these wrappers. Understanding this before you move (and timing any sales or withdrawals correctly) can prevent you from turning a tax-free investment into a taxable one.

“The worst cases I see are people who've already moved and are trying to fix things retroactively,” says Carl. “Sometimes we can help, but often the damage is done. They've triggered taxes, missed deadlines, or lost allowances they can never get back. It's heartbreaking because it was entirely preventable.”

The good news? All of this is avoidable. Professional tax planning before your move, even just a few months before, gives you time to structure your finances properly, time your move correctly, and make the most of the allowances and reliefs available to you.

Carl Turner, Co-founder of Expat Tax Thailand, commented:

“When it comes to protecting your money as an expat, it’s all about planning before you move, not after. Start by speaking to a tax advisor who understands both your home country and destination country rules, at least three to six months before your move date. They can map out the optimal timing for your relocation and any asset transfers.

“Keep detailed records of your time in each country, when you moved, and when you transferred assets. This documentation is vital if tax authorities ever question your residency status.

“Don't assume tax treaties will automatically protect you. You often need to actively claim relief. And remember, every expat's situation is different. What worked for your friend might not work for you. Get personalised advice based on your specific circumstances.”

About Expat Tax Thailand

Expat Tax Thailand is a tax advisory and filing service tailored specifically for expatriates living in Thailand, offering clear guidance on Thai tax obligations. They help clients understand, comply with, and optimize their tax positions, from simple to complex cases, via a secure online platform. Their services include essential, assisted, and expert tax filings, along with strategic tax planning, estate planning, and cryptocurrency compliance. They ensure personalized, English-speaking, responsive support with certified Thai accountants who specialize in expat tax.

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