Documentary letter of credit 是letter of credit（信用证）中的一种，跟单信用证。信用证是国际贸易中常用的支付结算方式，是指银行根据进口人（买方）的请求，开给出口人（卖方）的一种保证承担支付货款责任的书面凭证。在信用证内，银行授权出口人在符合信用证所规定的条件下，以该行或其指定的银行为付款人，开具不得超过规定金额的汇票，并按规定随附装运单据，按期在指定地点收取货款。

信用证根据其项下的汇票是否附有货运单据而划分为documentary credit （跟单信用证）和光票信用证（clean credit）。题主所问的即属于第一种，在国际贸易的货款结算中，绝大部分使用的就是跟单信用证，其两者具体的释义如下：

①跟单信用证(Documentary Credit)是凭跟单汇票或仅凭单据付款的信用证。此处的单据指代表货物所有权的单据（如海运提单等），或证明货物已交运的单据（如铁路运单、航空运单、邮包收据）。Documentary letter of credit is an undertaking of the bank, which has opened a letter of credit on request of a buyer (applicant) to pay an amount to the seller (beneficiary) as specified in the letter of credit upon the provision of documents by the seller (beneficiary) that meet the conditions of the letter of credit and confirm the shipment of commodities (the provision of services) within the prescribed time frame.

②光票信用证(Clean Credit)是凭不随附货运单据的光票(Clean Draft)付款的信用证。银行凭光票信用证付款，也可要求受益人附交一些非货运单据，如发票、垫款清单等。A clean letter of credit allows an applicant to issue drafts which must be paid on demand by the bank, without additional required documentation.

以下为相关示例：

例1：

It means Irrevocable documentary letter of credit open in United States dollars.

其系指以美元计价的不可撤销的跟单信用证。

例2：

Payment: By irrevocable documentary letter of credit opened through Bank of China and drawn at sight.

支付方式：凭中国银行开立的不可撤销的跟单即期信用证支付。