An aleatory contract is an agreement whose performance depends on an uncertain future event. Until that event occurs, one or both parties may owe nothing at all, and when it does, the value exchanged can be highly unequal.

How Aleatory Contracts Work

The defining feature is contingency. The parties agree up front, but the actual obligation to perform is triggered only if a specified, uncertain event happens. Both sides knowingly accept that the outcome depends on chance.

Common Examples

• Insurance: you pay premiums, but the insurer only pays out if a covered loss occurs. You might pay for years and collect nothing, or pay once and collect a large claim.
• Annuities: payments depend on how long the annuitant lives.
• Wagers: payment hinges entirely on an uncertain result.
• Options: the holder may or may not exercise, depending on future conditions.

Aleatory vs. Ordinary Contracts

In a typical contract, each side knows roughly what it will give and get. In an aleatory contract, the amounts exchanged are deliberately uncertain and potentially unequal. That imbalance is the point, not a flaw.

Are Aleatory Contracts Enforceable?

Yes, provided they meet the standard requirements of a valid contract and serve a lawful purpose (gambling contracts are an exception where prohibited by law). The uncertainty itself doesn't make the agreement invalid.

An aleatory contract is one of several specialized categories. To see how it sits alongside bilateral, unilateral, and other forms, read our guide to types of contracts.

Frequently Asked Questions

Is insurance an aleatory contract?

Yes. Insurance is the most common example: performance by the insurer depends on whether an uncertain, covered event occurs.

What's the difference between aleatory and conditional contracts?

All aleatory contracts are conditional, but the condition specifically involves chance or an uncertain event outside the parties' control, and the exchange of value is intentionally uneven.

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