The Convention of 5 October 1961 on the Conflicts of Laws Relating to the Form of Testamentary Dispositions (HCCH 191 Form of Wills Convention) improves the legal certainty of a will by designating, among a set of laws, the law of a State that governs the form of testamentary disposition. Under the Convention, a testamentary disposition shall be valid if its form complies with the internal law of either:
- the place where the testator made it;
- a nationality possessed by the testator;
- a place in which the testator had their domicile;
- the place in which the testator had their habitual residence;
- concerning immovable property, the place where the property is situated.
As a result, a foreign will made in compliance with one of these laws cannot be void because a form required by the law of another Contracting Party where the will is to be executed has not been followed. In practice, the Convention assists testators to dispose of all their heritage within a single will, including when the heritage is in different States.