5 CFR 731.303: Answer.

(a) Respondent's answer. A respondent may answer the charges in writing and furnish documentation and/or affidavits in support of the answer. To be timely, a written answer must be submitted no more than 30 days after the date of the notice of proposed action.

(b) Agency's answer. An employing agency may also answer the notice of proposed action. The time limit for filing such an answer is 30 days from the date of the notice. In reaching a decision, OPM will consider any answer the agency makes.