I work in an office with a fairly specific work-flow. My part of the work-flow is to inspect my coworker's work for accuracy before it is sent to the sales force in the field.
One of the people I audit is my immediate supervisor. Once in a while, they get upset when I send a document back for correcting. Sometimes I am accused of being insubordinate for requesting the item be corrected before I would sign off on it.
To be clear, these are factual type errors, not matter-of-opinion errors.
How can I address my superiors quality issues in a way that is professional and not insubordinate?