It is a private contract made in a verbal or written format. A declaration of the intent to marry and an acceptance of the terms are required as in other forms of marriage in Islam. According to Twelver Shia jurisprudence, preconditions for mut'ah are: The bride must not be married, she must attain the permission of her wali if she has never been married before, she must be Muslim or belong to Ahl alKitab (People of the Book), she should be chaste, must not be a known adulterer, and she can only independently do this if she is Islamically a non-virgin or she has no wali (Islamic legal guardian). The most authoritative view holds that if the stipulated period is not mentioned in the text of the contract, the marriage cannot take place and the contract is invalid. At the end of the contract, the marriage ends and the wife must undergo iddah, a period of abstinence from marriage (and thus, sexual intercourse). The iddah is intended to give paternal certainty to any children should the wife become pregnant during the temporary marriage contract.

Historically there were many types of marriages, used for various purposes, as opposed to a full marriage; in mut'ah some of the rights of the husband and wife are non-existent. This was primarily used by those who could not stay at home with their wife and traveled a lot. For example, a traveling merchant might arrive at a town and stay for a few months, in that period he may marry a divorced or widow, and they would take care of each other. When he has to leave to the next down, the marriage is over, and he might sign a mut'ah contract at his next place.
The Twelver Shias based on the Quran, hadith argue that the word of the Quran takes precedence over that of any other scripture, including the An-Nisa, 24, known as the verse of Mut'ah:

Also (prohibited are) women already married, except those whom your right hands possess: Thus hath Allah ordained (Prohibitions) against you: Except for these, all others are lawful, provided ye seek (them in marriage) with gifts from your property,- desiring chastity, not lust, seeing that ye derive benefit from them, give them their dowers (at least) as prescribed; but if, after a dower is prescribed, agree Mutually (to vary it), there is no blame on you, and Allah is All-knowing, All-wise. (Quran 4:24)

Today, mut'ah is used for various situations. People who get engaged will perform mut'ah first so they can speak to each other, hang out and get to know each other with conditions set by the woman and her family. Relationships could be forbidden if pursued, so performing mut'ah under a contract for a set period of time with a dowry protects the woman.
A divorced woman can engage in relationships through mut'ah before deciding if she does or does not want to remarry another man.

Some Muslims and Western scholars have stated that Nikah mut'ah is Islamically void attempts to religiously sanction prostitution which is otherwise forbidden. The schools of Sunni law prohibit mutʿa based on the Sunna (lived tradition and example) of the Prophet Muhammad, who declared after the battle of Khaybar in 629 CE that temporary marriages were no longer valid.