A term of contract law to distinguish advertisements or merchandise displays from formal contract offers.
An offer exposes the offeror to a contract if it is accepted by the offeree; an invitation to treat does not.
Halsbury (2007):
"An invitation to treat is a mere declaration of willingness to enter into negotiations; is is not an offer, and cannot be accepted so as to form a binding contract."
In Duhaime's Offer and Acceptance (published at duhaime.org/LegalResources/Contracts/tabid/339/articleType/ArticleView/articleId/89/Part-4-Offer--Acceptance.aspx):
"An offer must be a clear, unequivocal and direct approach to another party to contract. For this reason, advertisements, catalogues or store flyers are not offers. Nor is a "for sale" sign on a used car.
"The law calls these invitations to treat; essentially invitations to the general public to make an offer on a particular item. But, even here, there have been exceptions. For example, in a 1856 case, an advertisement of train rates was held to be a valid offer. Much depends on the wording of the 'invitation'."
An invitation to treat is merely an announcement to other that a person is prepared to entertain an offer for a certain thing or service.
The invitation to treat may provide minimal terms of a proposed offer.
In Chitty on Contracts (2004), the editors point out that:
"As a general rule, a display of goods at a fixed price in a shop window or on a shelf in a self-service store is an invitation to treat and not an offer. An offer may be made by a prospective buyer. At this stage, the retailer may accept or reject that offer.
"Similar principles would seem to apply where a supplier of goods or services indicates their availability on a website: that is, the offer would seem to come from the customer (eg. when he clicks the appropriate button) and it is then open to the supplier to accept or reject that offer."