Reference List -- APA
In APA format, include the year, number and name of the form you are citing. Also include the catalog number after the form name -- note this is not the IRS form number. The catalog number is either on the first page of the form or on one of the bottom rows of a form. List both the IRS and the agency it is a part of -- the Department of the Treasury. For instance, you might cite an IRS document:
U.S. Department of the Treasury. Internal Revenue Service. (2015). 1099: Miscellaneous income (Cat. No. 14425J). Washington, DC: U.S. Government Publishing Office.
If you found your document online, include the form's URL in place of the publication location information:
U.S. Department of the Treasury. Internal Revenue Service. (2015). Publication 17: Tax guide 2014 for individuals (Cat. No. 10311G). Retrieved from http://www.irs.gov/pub/irs-pdf/p17.pdf.
Reference List -- MLA
In MLA format, you will include United States at the beginning of your citation, and abbreviate the department name. The date is included after publisher's information, and the catalog number is not required. Include the format type -- print or Web -- after the date:
United States. Dept. of the Treasury. Internal Revenue Service. 1099: Miscellaneous Income. Washington: GPO, 2015. Print.
MLA does not require you to include a URL for web publications, however you include the date you accessed your source after the format type. Include the website name before the date:
United States. Dept. of the Treasury. Internal Revenue Service. Publication 17: Tax Guide 2014 For Individuals. Internal Revenue Service, 2015. Web. 30 March 2015.
Referencing IRS Documents In-Text
When referencing your form in-text in APA, include the name of the organization, the year of publication and the page number, if applicable. For example: (Internal Revenue Service, 2015, p. 15) If you cite an IRS source multiple times, use an acronym for all citations past the first: (IRS, 2015, p. 57)
In MLA, your in-text citation will only include the name of the author and the page number. MLA encourages useful abbreviation, so you can use the acronym for all in-text citations: (IRS 15)