On Jul 26, 5:52 pm, mlion wrote:
I'm interested to see the TIL position on calculating the APR.

The Truth in Lending method of computing APR is essentially the IRR.
And I might note that it is the Excel function IRR(), not XIRR(). A
(US) loan APR is a nominal rate, not a compounded rate like the APY.

You can find all of Reg Z at
http://www.fdic.gov/regulations/laws...6500-1400.html .
The link to Appendix J takes you to
http://www.fdic.gov/regulations/laws...ndixjtopart226
..

Unfortunately, the presentation and confusing terminology leave much
to be desired, IMHO . But you might recognize the "general equation"
as an NPV formula, where the left side is the NPV of the advances
(e.g. loan amount) and the right side is the NPV of the payments.

Thanks again for your assistance.

My pleasure. Helping others is always an education for myself, too.