A Borrower Pays €100. Where Does the Money Go?

This story was originally published on HackerNoon at: https://hackernoon.com/a-borrower-pays-euro100-where-does-the-money-go. How payment allocation exposes a deeper Financial Product Engineering challenge: turning financial intent into precise, reliable, evolvable software behavior. Check more stories related to finance at: https://hackernoon.com/c/finance. You can also check exclusive content about #fintech, #financial-software, #system-design, #lending, #open-source, #apache-fineract, #hackernoon-top-story, #where-does-the-money-go, and more. This story was written by: @adamsaghy. Learn more about this writer by checking @adamsaghy's about page, and for more stories, please visit hackernoon.com. A €100 borrower payment has no universal destination — its allocation across past-due, due, and future installments, and across principal, interest, fees, and penalties, is a policy decision. Financial Product Engineering turns a lender's intent into precise, deterministic, evolvable software behavior: configurability with exact semantics, chronological event processing, rule changes that preserve existing contracts, and testing lifecycles, not calculations.