1. Compliance requirements: According to relevant laws and regulations, postal savings vouchers, as financial vouchers, must meet certain format and signature requirements, and managers and auditors, as key personnel in the voucher preparation process, must sign or seal according to regulations to ensure the compliance and legality of vouchers.

2. Prevention of forgery: certificates of deposit lack the signatures and seals of managers and auditors, and are easy to be forged or tampered with, which will threaten the safety of customers' funds and the reputation of banks.