Answer
A qualified opinion is issued when the auditor concludes misstatements are material but not pervasive, or when they cannot obtain sufficient appropriate evidence about a matter that is material but not pervasive (a limited scope limitation). The report uses 'except for' language, identifying the specific matter while confirming the rest is fairly presented.
Real-world example Unable to verify one material inventory location, the auditor issues an 'except for' qualified opinion on that matter only.