The United Kingdom tax system basically seeks to tax the worldwide income and gains of an individual resident in the UK during a tax year. It will also seek to tax all UK source income. This rule is often amended by the effect of a double taxation agreement between the UK and another country which might otherwise also wish to tax the income under its own tax rules.

The rules can be complicated. An individual will always be classed as resident in the UK in a tax year if they have been in the UK for more than half of that year. They will also be classed as resident if they average more than 90 days spent in the UK during a continuous period of 3 tax years.

The domicile of an individual is the general legal status which regulates his personal relationships, eg birth, marriage and succession. There can only be one domicile at any one time.

An individual may be resident but not domiciled in the UK in a tax year. As such, he will be taxed on his UK income and gains but not on income and gains arising abroad unless these are brought into the UK.