@taxcurious2 wrote:
So nobody knows which formula is used? surely the IRS knows, at least the person who programmed the computer that charges the interest.
Of course, but you are asking for the exact programming specifications and test values. We don't have that. There are other IRS resources, for example:
https://www.irs.gov/irm/part20/irm_20-002-005r
https://www.irs.gov/payments/interest
If you want to know more, you may need to ask an enrolled agent.
