A marriage license is a document issued, either by a church or by a government authority which authorizes a couple's union. There are legal requirements that go along with attaining a valid marriage certificate, many of which require you to present documentation to a government agency to prove the marriage is legal. Today, you are required legally to have a marriage certificate to prove your legal union and it also may serve as a record of marriage if it is signed and notarized. In order to be a valid and legal marriage certificate, it must be signed by the couple, witnesses (if applicable), officiant, and, in some cases, a notary.