L/C means Letter of Credit. It is a document in which your bank gives a guarantee that it will pay a certain amount of money upon the delivery of certain conditions, or presentation of certain documents.
In practice this means, for example, that you order some goods, you ask your bank for an L/C with the price of the order, and when the supplier presents some proof of their delivery, like the Bill of Lading of the forwarding company, he can go to his own bank and get the amount of the L/C. It is a payment method that is reasonably safe for both supplier and buyer. Inform yourself at your bank on more details.
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