邮资凭证 meaning in English

postage certificate

Article 18 . postage certificates sold shall not be cashed in postal enterprises or their branch offices
第十八条售出的邮资凭证不得向邮政企业及其分支机构兑换现金。
Article 16 . the payment of postage on various postal materials shall be indicated by postage certificates or by postmarks showing postage paid
第十六条各类邮件资费的交付，以邮资凭证或者证明邮资已付的戳记表示。