Dave wrote:
A simple example:a $30,000, 20 year mortgage at 7.499% yields monthly
payments (using the standard Excel PMT function, as well as just about any
other mortgage calculator around) of $241.66. Looking at the resulting
amort schedule at say 36 months, shows the principle reduced to +/-
$27,887.50.

The Rembrandt calc yields monthly Payments of $241.77, and with the
principle reduced to only $28,059.74.

For what it's worth, a payment of $241.77 and a balance of $28,059.74
after 36 months corresponds to a 27-year loan of $30,000 at a nominal
annual rate of 8.75346%. (Sorry, but that precision is necessary to
get a payment amount that rounds to $241.77 __and__ a balance that
rounds to $28,059.74.)

This leads me to speculate that perhaps you are looking at an ARM of
$30,000 with a 3-year initial term at 7.499% and index and margin
parameters such that the estimated adjusted rate is 8.75346%, and
somehow the latter percentage got associated with the computation for
the 3-year initial term -- or some other human error along these lines
occurred

Does that ring any bells?

However, take a look at
http://www.bankerssystems.com/ARTA/BL_HMDA.htm
This is the parent company of CCH. They have indeed sold to the financial
market place a very proprietary routine which does exactly as I said -
increases monthly payment and decreases principle reduction.

I do not see anything on that web page that discusses a "proprietary
routine" that has those objectives. Can you explain a little more
about where you are reading that claim?

That web page talks about software for aiding lenders in reporting HMDA
rate spreads. Of course, the software implementation might be
proprietary. But the methodology is not; it is defined by US federal
regulations.

In any case, I cannot find any mention of a loan calculator per se,
much less a loan calculator with unique goals.

The Rembrandt web page does refer to an HOEPA calculator, which might
encompass normal loan computations. And the purpose of recent HOEPA is
to modify (raise or lower) certain triggers (of lender requirements)
related to HOEPA loans. But I do not think that should affect the
normal loan computations. In any case, this methodology is not
proprietary either; rather it is defined by US federal regulations.

I wonder if you are confused and reading some of the HMDA and HOEPA
explanations as proprietary claims. In any case, I do not think that
would explain the numerical disparities in the loan computations that
you described.