How to distinguish these two? Sometimes the same item appears in both parts of an IPS doesn’t it?
specific to reoccurring exp. if there is a question on calculating required rate of return for the return objective put it there. If there required rate of return isn’t asked, put it in liquidity constraint. if you aren’t sure, put it in both.
What helped to me, I first determine and state all constraints found in text including liquidity constraint. The idea is that constraints condition R&R objectives. As AlmostDone said, usually you are asked to calculate rate of return while under constraint you just have to put textual descriptions.