Iowa Admin. Code r. 657-35.16
An answer may be filed within 20 days of service of the notice of hearing and statement of charges. An answer shall specifically admit, deny, or otherwise answer all material allegations of the statement of charges to which it responds. It shall state any facts supporting any affirmative defenses and contain as many additional defenses as the respondent may claim. An answer shall state the name, address and telephone number of the person filing the answer. Any allegation in the statement of charges not denied in the answer is considered admitted. The presiding officer may refuse to consider any defense not raised in the answer which could have been raised on the basis of facts known when the answer was filed if any party would be prejudiced.
Iowa Admin. Code r. 657-35.16