An annex and an appendix are both forms of addendums to a main document. An appendix contains data that cannot be placed in the main document and has references in the original copy or file. An annex, on the other hand, is usually a standalone document that offers additional information than contained in the main document.
Comparison chart
 | Annex | Appendix |
|---|---|---|
| Definition | Annex is an addition to a document. | Appendix is an addition made towards the end of a thesis. |
| Usage | a term used mostly in business models and ideas. | a term used in the research field. |
Relation to the main document
An appendix cannot be submitted without the main copy. The aim of an appendix is to add greater details, visuals and examples for better understanding of the main copy. An annex, however, is different from an appendix in that it can be considered without the main text. It cannot be added to the main text but still has importance as regards the original copy.
Authors of an annex vs an appendix
Appendices are usually written by original authors whereas annexes can be written by outside party.
Envy 
Principal 
Avenge
Comments: Annex vs Appendix