Answer:
You are not going to find any documentation. I am also unsure by what you mean. You mean you have a joint credit application and then one of the borrowers withdraw leaving only a single applicant? How you handle that situation is an operational issue as to whether you allow the single applicant to continue or you treat it as a withdrawn application and require the single party to reapply. If you are in a situation where the joint applicants will not be approved, but one of the applicants if applying alone could be approved, then you owe one of them an adverse action notice.