This paper studies the decision of firms to extend trade credit to customers and its relation with their financing decisions. We use a novel firm-level database with unique information on market power in both output and input markets and on the amount, terms and payment history of trade credit simultaneously extended to customers (account receivables) and received from suppliers (account payables). We find that suppliers with relatively weaker market power are more likely to extend trade credit and have a larger share of goods sold on credit. We also examine the importance of financial constraints. Access to bank financing and profitability are not significantly related to trade credit supply. Rather, firms that receive trade credit from their own suppliers are more likely to extend trade credit to their customers, and to "match maturity" between the contract terms of payables and receivables. This matching practice is more likely used when firms face strong competition in the product market (relative to their customers), and enjoy strong market power in the input market (relative to their suppliers). We also find evidence that firms match the ex-post timing of payments, i.e. firms that receive payments early from customers are significantly more likely to remit early to suppliers. These results highlight the importance of supply chain financing for market competition and growth.