Domicile is often confused with residence, but it is quite distinct
The law of domicile is highly complex and has wide-ranging consequences on an individual’s tax position, as the recent furore surrounding Akshata Murty illustrates, but for most British nationals here in Portugal, domicile is a key factor for UK Inheritance Tax (IHT).
Individuals only have one domicile at a time and a very loose definition is ‘where you have a permanent home’. In my experience, this is often misunderstood and individuals who thought they were ‘definitely non-UK domiciled’ after living in Portugal for several years learn that in fact, they are very much still UK domiciled.
The are several types of domicile, namely ‘Origin’, ‘Choice’, ‘Dependence’ and ‘Deemed’ but here I will focus on the first two. Firstly, ‘Origin’. This is acquired at birth, usually from your father (or your mother if they were not married at the time of your birth). This is never fully lost but can be suspended by acquiring a new domicile of choice, but it is adhesive and will revive if the new domicile is lost.
Acquiring a domicile of choice involves forming a clear and fixed intention for a new country to be your permanent home, and therefore actually requires permanent residence.
Being non-UK domiciled is highly advantageous for UK IHT
The worldwide estates of UK domiciles are assessed for IHT in the UK, even if you live elsewhere. For non-UK domiciles, generally only UK based assets are assessed. It is worth noting here, that assets that derive their value from the UK but are held elsewhere e.g. company shares, will be deemed to be UK assets.