When you're writing a long or complex paper, which is common in American Psychological Association (APA) style, you may need to include some information that doesn't quite fit into the main body of the document. In this situation, you can present the supplemental material in an appendix or two, which can be mentioned in the primary text. If the readers are interested in the additional information, then they can browse the appendices. Of course, the appendix, just like any other section of the paper, must be formatted in a certain way in order to follow APA style accurately.
Place the appendix on a fresh page, immediately after the last page of text in your paper. Start the appendix at the top of that new page.
Label the appendix by simply typing "Appendix," with only the first letter capitalised, at the top of the page. According to the Publication Manual of the American Psychological Association, you should centre this title, but do not make it bold, italicised, underlined, or larger than the rest of the text. If your paper includes more than one appendix, then each appendix should be assigned a letter (not a number): Appendix A, Appendix B, etc. That letter should be included in the title. (If you only have one appendix, then don't include a letter.)
Format the visual contents of the appendix like they would be formatted in the paper's body. All tables, figures and equations should be labelled and numbered. However, each label and number should include a letter that corresponds to the appendix rather than the main text. For example, in the first appendix, the first table should be labelled "Table A1," and the first figure should be labelled "Figure A1." If there's a second appendix, the fifth figure in it would be labelled "Figure B5"; similarly, the first equation in the third appendix would be labelled "Equation C1."
Format all plain text in the appendix as it would be normally formatted. The text should be double-spaced and the font should be a serif typeface (such as Times New Roman) in a standard size (usually 12). The very first line of the appendix differs from normal rules; it should begin flush left, rather than indented. Succeeding paragraphs, however, should begin with a 1/2-inch indentation, like normal APA paragraphs.
Mention the appendix in the main text of the paper, referring to it by its capitalised title (such as Appendix B). If you refer to more than one appendix at the same time, remember that the plural spelling of "appendix" is "appendices." For example, "See Appendices C and F for samples of the survey administered to the participants."
The APA Manual warns against including lengthy appendices. If you have a large amount of supplemental material, then you should consider using an online archive to provide the information to readers, rather than using an appendix.