What is the term used to describe the situation when a person dies without a valid will?

The answer is intestacy.  it means that when a person dies and has property that is worth more than the total of their obligatory debts and funeral costs, with making a legal will or any compulsory declaration. This can also apply to situations where there is a will but is only applicable to a part of the estate while the rest of the estate becomes the intestate estate. Intestacy law also known as the law of descent and distribution decides who is eligible for the property from the estate under inheritance rules.