1 Pa. Code § 35.35
Answers to complaints and petitions, other than petitions to intervene and petitions of appeal from delegated actions of subordinate officers, shall be filed with the agency within 20 days after the date of service, unless for cause the agency with or without motion shall prescribe a different time, but in no case may an answer be required in less than 10 days after the date of service. Answers to petitions of appeal from delegated actions of subordinate officers shall be filed with the agency within 10 days after the date of service. A respondent failing to file an answer within the applicable period shall be deemed in default, and relevant basic facts stated in the complaint or petition may be deemed admitted. Answers shall be in writing, and so drawn as fully and completely to advise the parties and the agency as to the nature of the defense. They shall admit or deny specifically and in detail each material allegation of the pleading answered, and state clearly and concisely the facts and matters of law relied upon.
1 Pa. Code § 35.35
This section cited in 1 Pa. Code § 35.9 (relating to formal complaints generally); 4 Pa. Code § 60.6 (relating to procedure); 7 Pa. Code § 179.14 (relating to answers to complaints, petitions, motions and other filings requiring a response); 12 Pa. Code § 11.9 (relating to answers to complaints and petitions); 25 Pa. Code § 1021.74 (relating to answers to complaints); 28 Pa. Code § 1230.39 (relating to timeliness of Notice of Appeal); 34 Pa. Code § 111.15 (relating to no other pleadings allowed); 34 Pa. Code § 111.23 (relating to answers); 34 Pa. Code § 111.34 (relating to answers to petitions); 34 Pa. Code § 131.33 (relating to answers except to answers for joinder and challenge proceedings); 34 Pa. Code § 131.36 (relating to joinder); 34 Pa. Code § 131.121 (relating to penalty proceedings initiated by a party); 37 Pa. Code § 171.44 (relating to supporting legal authority); 37 Pa. Code § 197.11a (relating to motions and petitions); 40 Pa. Code § 17.13 (relating to protests/intervention procedure); 49 Pa. Code § 19.35 (relating to subsequent pleadings); 52 Pa. Code § 5.61 (relating to answers to complaints, petitions, motions and preliminary objections); 52 Pa. Code § 5.405 (relating to effect of pleadings); 52 Pa. Code § 1005.41 (relating to answers to complaints, petitions, motions and other filings requiring a response); 52 Pa. Code § 1005.145 (relating to effect of pleadings); 55 Pa. Code § 41.71 (relating to answers generally); 58 Pa. Code § 493a.5 (relating to answers to complaints, petitions, motions and other filings requiring a response); 61 Pa. Code § 703.2 (relating to petition content); 61 Pa. Code § 703.8 (relating to timeliness of submissions); and 67 Pa. Code § 491.6 (relating to notice and conduct of hearing).