What is insurable interest, and why does it matter?

A legally recognised relationship between the insured and the subject of the insurance, such that they would suffer a loss if the insured event occurred — and without it, a policy is not insurance but a wager.

Why the requirement exists. Two distinct reasons, both practical:

To prevent gambling. Without insurable interest, anyone could take out a policy on anything — a stranger's house, a ship they have no connection to — and profit from its destruction. Historically this happened, and eighteenth-century legislation addressed it directly.

To remove the incentive to cause the loss. A person who would gain from a house burning down, without losing anything, has an obvious motive. Requiring that they would genuinely suffer removes it, which is the more important reason.

What creates insurable interest:

Ownership of property.

A legal or equitable interest — a mortgage lender in a mortgaged property, a lessee in leased premises, a bailee in goods held.

Contractual liability for something.

Potential legal liability to others.

In life insurance, an unlimited interest in your own life; an interest in a spouse or civil partner's life; and an interest in another person's life to the extent of a financial dependency or obligation — a creditor in a debtor, an employer in a key employee.

When it must exist:

Property insurance — generally at the time of the loss. Selling a house means losing insurable interest in it.

Life insurance — at inception of the policy, and it need not continue. This is why a policy on a spouse remains valid after divorce, which surprises people.

Marine insurance has its own statutory treatment.

What follows practically:

You cannot insure something you do not own or have an interest in, which is why insuring a car registered to and owned by someone else raises questions — and why fronting, where a parent insures a car mainly driven by a child, is a misrepresentation with serious consequences.

Joint owners should be named.

Tenants insure contents, not the building; landlords insure the building.

Businesses need interest in what they insure, which affects group arrangements and contractor obligations.

Reform has narrowed the requirement's practical significance in some contexts, and it remains a foundational principle.

General information, not advice.