The Duchess of Sussex could be barred from re-entering the US in the future if she chooses to renounce her citizenship.

The US government has started enforcing provisions of 1986 legislation allowing the country to exclude tax "refugees" - Americans who drop their citizenship to avoid paying US tax on earnings they make overseas.

According to the State Department, a small number of former Americans have already been barred from re-entering, and the move could present a dilemma for the Duchess and her son Archie (a dual US-UK citizen) if they choose to become solely British citizens.

A spokesman for the State Department confirmed that renouncing US citizenship for tax purposes were grounds for denying re-entry.

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The United States taxes its citizens irrespective of where they live. Anybody born in the US is classified as a US citizen until they renounce their nationality.

This has created a cohort of "accidental Americans" who have been burdened with tax liabilities even if they left the country shortly after they were born. The biggest financial blow is when an American sells a home.

The profit is taxable and treated separately from other income.

One victim was Boris Johnson, who was born in New York, and had to pay a substantial tax bill on the profit he made on the sale of his home in London in 2014.

Mr Johnson, who left the US at the age of five, renounced his American citizenship in 2016.

Even though he was deemed to have done so for tax reasons, he would not face exclusion from the US should he become prime minister, as the provisions do not automatically apply to diplomatic visas