For anyone who lives and earns across borders, tax stops being a single-country matter and becomes a question of how systems interact. You do not have to become an expert. But you do need to understand a few core principles well enough to know when — and it is usually before you move — to get proper advice. This is a plain-English overview of the basics, not tax advice; the specifics always depend on your circumstances and jurisdictions.
Residency and domicile are not the same thing
These two words are often used interchangeably, and confusing them causes real problems.
- Residency is generally about where you currently live, often determined by day counts and specific statutory tests. It can change relatively quickly when you move.
- Domicile is a deeper, stickier concept in some systems — broadly tied to your permanent home or long-term connection to a country. It can persist even after you have moved away, and it can influence how certain taxes apply.
The practical point is that your tax position is shaped by both, and by how each country defines them. Two people in seemingly identical situations can be treated very differently depending on these tests.
Double-tax treaties exist to stop you being taxed twice
When two countries could each claim the right to tax the same income, a double-tax treaty between them typically sets out which one takes precedence, or how relief is given. These agreements are the reason internationally mobile people are not routinely taxed twice on the same money — but they are detailed, they differ from one country pair to another, and they do not cover every situation automatically. Assuming a treaty will quietly solve everything is a common and costly error.
Timing is often the decisive factor
In cross-border tax, when you do something frequently matters as much as what you do. The date you become or cease to be resident, the moment you realise a gain, the point at which you transfer an asset — all of these can change the outcome. A decision that is efficient in one tax year can be far less so if made a few weeks earlier or later. This is why planning ahead of a move is so much more powerful than reacting after it.
The principle: advice before the move, not after
The single most valuable habit in cross-border finance is simple: get advice before you move, not after. Once you have crossed a border and triggered a residency change, many of the most useful options have already closed. Beforehand, you have room to sequence things sensibly. Afterwards, you are often managing consequences.
This is structure before solutions applied to tax. Start with reality — where you are, where you are going, when. Establish direction. Then build the structure, with proper advice, so the arrangements fit the rules rather than colliding with them. The weak link in most international financial lives is a move made before the tax position was understood.
None of the above is definitive for your situation, and it is not meant to be. Tax is one of the areas where general information can only take you so far, and where qualified, jurisdiction-specific advice earns its keep.
This article is general information, not personal financial advice. Everyone’s situation is different — book a conversation to talk through yours.