Legal Definitions - mail box rule

The mail box rule is a legal principle that states that a written offer or acceptance of an offer is valid if sent in the mail, with postage, within the time in which the offer must be accepted. This applies unless the offer requires acceptance by personal delivery on or before the specified date. The rule may also apply to mailing payments of insurance premiums when due.

For example, if a company sends a job offer to a candidate and specifies that the offer must be accepted within 10 days, the candidate can accept the offer by sending an acceptance letter in the mail within the 10-day period. The acceptance is considered valid as soon as the letter is mailed, even if the company has not yet received it.

However, it is important to note that relying solely on the mail box rule can be risky. The party awaiting the acceptance or payment may cancel the offer if there is no response in hand when the time runs out.