Programs can choose between 3 options when requesting a document - required, conditionally required and optional.
If a program sets a document as required, the applicant must assign this document to this programs application, otherwise their application may be deemed incomplete.
Conditionally required means that this document will be required under certain conditions. These conditions will be specified by the program in their program description.
Finally, if a program sets a document as Optional, it is not mandatory to assign this document.
If a program sets a document as conditionally required or optional and the applicant does not have this document, the applicant cannot be penalized.
Note: some documents can only be set as conditionally required or optional as not every applicant would be eligible to receive this document.