I believe that your problem can be solved through the use of financial functions, specifically the PMT function on Anaplan: https://help.anaplan.com/07d126f7-dd4d-4510-b15d-add22fc527fd-PMT Considering financial theory, the IRR simply represents the rate of return on an investment for which the Net Present Value (NPV) is zero. For this, we can force the Present Value (PV) = 0. Consider a simple example of making periodic payments specified time frame (say, a yearly payment over 5 years) and receiving a lump sum amount at the end of 5 years (FV) In financial terms, the example above can be formally represented as: Present Value (PV): Forced to be 0 for calculation of IRR Payment (PMT): The 5 periodic payments made annually Number of Periods (N): 5, since for 5 years you make a payment annually Future Value (FV): The lump sum promised to you at the end of the period for your investment Interest Rate (R): The rate of return Out of the 5 parameters above, if you have any 4 already known to you (or are going to input them), calculating the 5th one is straightforward. My understanding of your problem statement is that you would like to input the IRR, hence you have the R. Since you will be calculating IRR, the PV will be set to 0. The number of periods (N), it appears, is known. I am assuming there is either a FV or a PMT also available; and the left over 5th parameter is the missing value to be calculated. Also, please note that a sign-change between FV and PMT is important here. Imagine receiving a $10,000 investment later (FV): since it is "cash in", we will represent it as 10000. Meanwhile, the periodic payments you make (PMT) will hold a negative sign, since it is "cash out". Or vice versa. By formulating your problem in terms fitting the general financial functions available, I believe a solution can be arrived at. Note, there are multiple ways to formulate a problem (for instance, instead of PV = 0, we could go with FV = 0 and flip the direction of calculation, which would be more relevant for a different kind of use case) and the specifics would depend entirely on your use case.

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