FundBox is one of a group of US B2B lenders in business to help companies maintain cash flow while awaiting outstanding payments. Unpaid invoices are a problem for small businesses who may wait from 30 to 90 days for payment, even after rendering goods or services. FundBox uses a revolving credit model to allow these businesses to receive instant payment for their choice of invoices. This credit is repaid when the original client pays off the invoice. Fundbox also offers a line of credit.