Letters of guarantee is a written undertaking issued by the bank at the request of one of its customers, in which the customer acknowledges that the bank will pay a financial value in favor of the entity to which the guarantee is issued, in case the value of the payment is claimed without reference to the customer or the customer opposes it. The customer also acknowledges the renewal of the letter of guarantee, but provided that the customer pays the bank the financial value at any date no later than the due date indicated in the letter of guarantee.