To cite a last will and testament, which is an unpublished legal document, follow the MLA format template. A basic entry should include a description of the will in the “Title of source” slot and the date the will was signed in the “Publication date” slot:

Last will and testament of John Smith. 12 Aug. 1967.

If it will be useful for your reader to know who notarized the document, list the notary’s name in the “Other contributors” slot:

Last will and testament of John Smith. Notarized by Jane Baker, 12 Aug. 1967.

If the will is clearly written by the individual whose estate it details—say, in the example of a handwritten will—include the writer in the “Author” slot:

Villanova, Jaime. Last will and testament. 15 Oct. 1934.