A series D round of venture capital funding is the stage in a company's life when it has proven its concept and business model and is ready to scale up. The company has typically achieved some significant milestones, such as gaining market share or turning a profit. At this stage, the company will have raised money from earlier rounds of funding and now needs to secure additional investment from venture capitalists in order to grow rapidly. The amount of money raised in a Series D round can vary significantly, depending on the size and potential of the company.