irr-series: closed-form internal rate of return for level and growing annuities
Year: 2026
Type: software
Abstract: Reference implementation and certification harness for a three-step, closed-form method that returns the internal rate of return of a level or growing ordinary annuity correct to two decimal places in a fixed number of steps, on both the profit and the loss branch, with no iteration and no convergence test. The deposit contains irr_series.py, the three steps together with the growing-annuity reduction and an independent bisection reference, and certify.py, which builds a 45,716-case battery over n in {1,...,100} and r in [-40%, +80%] and regenerates every numerical result reported in the accompanying article. The random component is fixed by a stated seed. There are no third-party dependencies.A companion workbook, irr_series_workbook.xlsx, carries the same method as live spreadsheet formulas: a calculator, the ten worked cases checked against Excel's own IRR, a 110-case accuracy test, the growing-payment reduction, and the whole method folded into a single cell.
Author: P N, Shakthi Vananth
Institution: Indian Institute of Management Jammu
Language: English
Subfield: Accounting
Domain: Social Sciences
Open Access status: green
OpenAlex ID: W7204199876