Getting the business involved in testing

The business side authors the software requirements. Then they got thrown "over the wall" to development. Design, component development, developer testing, integration and deployment happen before the business returns to review the final product. And guess what? It works, but it's not what we asked for. How can we avoid this trap, and get the business side to take deeper responsibility for testing? And what does it cost us to not have the business involved in testing?