The section 704(b) allocation Regulations contain a highly complex safe harbor, the substantial economic effect rules. If an allocation fails to comply with the safe harbor, it will only survive scrutiny if it is in accordance with the “partners’ interests in the partnership” (PIP). Given the complexity of the safe harbor, one might expect the PIP Regulations to be similarly complex, but nothing could be further from the truth. The PIP Regulations are, by tax standards, concise and straightforward. Some have argued that the PIP Regulations do not provide enough guidance, and that a more complex and comprehensive set of regulations would be preferable. In this Article, I argue that judges have made successful use of the PIP Regulations, and that a more complex set of PIP Regulations would achieve little and indeed might cause more problems than they solve. Accordingly, I argue against any substantial amendment to the PIP Regulations, though I would provide a safe harbor for target allocations.