<p>This study develops an integrated supply chain model to coordinate production planning, pricing, and discount promotion decisions under sustainability regulations and trade credit financing. In the proposed framework, a capital-constrained manufacturer receives trade credit from an upstream supplier, allowing deferred payment for raw materials at a specified interest rate. To comply with environmental regulations, the manufacturer invests in green technology to reduce carbon emissions arising from inventory holding and energy consumption. The model further accounts for product deterioration and time- and price-sensitive demand, which reduce product value and market demand over the sales horizon. Given that pricing, promotion, and production decisions are inherently interdependent in practice, this study simultaneously optimizes production uptime, regular and discounted prices, discount timing, cycle length, and green investment level. Different temporal relationships between production and promotion periods are explicitly examined, resulting in multiple operational subcases. Analytical properties of the model are established through a set of theorems and lemmas that guarantee the existence and uniqueness of the optimal solutions. Numerical experiments and sensitivity analyses are conducted to evaluate the proposed framework and to derive managerial insights. The results demonstrate that coordinated pricing and discount promotion strategies significantly enhance total supply chain profit compared with mono-pricing policies, particularly for perishable products. Moreover, trade credit is shown to play a strategic role in supporting operational coordination and sustainability investments. Overall, the study provides a comprehensive analytical foundation for integrating operational, financial, and environmental decisions in sustainable supply chain management.</p>