Constrained loan refers to the buyer's credit. Buyer's credit is a loan directly provided by the bank of the exporting country to a foreign importer or importer's bank. The additional condition is that the loan must be used to buy goods from creditor countries, thus promoting the export of goods. This is the so-called binding loan. If the imported goods are needed by the national policy to encourage the development of the industry, then it is easier to apply for loans, and the buyer's credit is guaranteed by the national credit.

Buyer's credit can not only enable exporters to obtain loans quickly and reduce risks, but also enable importers to know more about the costs other than the price of goods, which is convenient for them to bargain with exporters.

No matter whether it is lent to the importer or the importer's bank, the buyer can pay the seller immediately after obtaining the loan, thus promoting the transaction and expanding the export.

Exporters are also happy to use buyer's credit. Because exporters have achieved the goal of withdrawing funds quickly. Moreover, it will not cause a large number of "accounts receivable" in its accounting statements like seller's credit, because it may cause a bad impression on the enterprise by outsiders. At the same time, compared with seller's credit, buyer's credit saves exporters a lot of trouble in calculating, considering and passing on various expenses.