When the Associate Director determines that subchapter II of chapter 83 of title 5, United States Code, appears to prohibit payment of annuity, he shall notify the annuitant in writing of his intention to withhold payment of the annuity. The notice shall set forth the reasons for this determination. The notice may be served by registered or certified mail and shall inform the annuitant that he is entitled to submit an answer and request a hearing. [34 FR 17618, Oct. 31, 1969]