Hi Xamit Kadirbekov, Thank you very much for raising awareness about this issue. I have created the below story, you can use it to raise a PR with the enhancement: https://issues.apache.org/jira/browse/FINERACT-2809
Please let us know if you are facing any issues! Regards, Adam Saghy > On Sep 5, 2026, at 7:41 PM, Khamit Kadirbekov <[email protected]> wrote: > > Hello Fineract developers, > > I found a reproducible mathematical defect in the public > FinanicalFunctions.nop() helper. Its non-zero-rate branch is not the > algebraic inverse of the adjacent pmt() function. > > Minimal round trip: > rate = 0.01 > periods = 12 > principal = 1000 > future value = 0 > type = false > pmt(...) = -88.848788678342 > current nop(...) = 7 > expected nop(...) = 12 > > A repository-wide search found no current call site for nop(), so I am > treating this as a dormant library defect rather than claiming production > loan impact. > > I prepared a focused correction and regression tests in a public fork: > https://github.com/kadyrbekovhamit-cyber/fineract/commit/6980e1377ce2e5a1eaf0586e628b27bb64dd8c26 > > The proposed inverse is: > A = emiAmount * (type ? 1 + rate : 1) > growth = (A - rate * futureValue) / (A + rate * principal) > N = log(growth) / log1p(rate) > > The corrected implementation passes 33/33 direct PMT/NOP round trips across > zero and non-zero rates, both payment timings, and a non-zero future value. A > JUnit test is included. The full Gradle target could not run locally because > this checkout requires JDK 25 while the available JDK is 26. > > The contribution guide requires a FINERACT JIRA key in the PR title and > commit. ASF JIRA does not allow guest issue creation, so could a maintainer > please advise whether this should receive a ticket, or create/link one if the > correction is wanted? I can then update the commit title and open the > conforming PR. > > Best regards, > Xamit Kadirbekov > GERO Research
