scheduled loan payment setup question

[Brian Smith]

On 24 Dec 2002 10:00:50 +1100
  Conrad Canterford <conrad@mail.watersprite.com.au> 
wrote:

>And this demonstrates the fundamental problem that any 
>loan druid is
>going to have. These two options may work for some (maybe 
>even most)
>people around the world, but they by no means cover all. 
>In Australia,
>we have loans that calculate interest daily, but credit 
>it monthly, we
>have loans structured around fortnightly payment and 
>interest intervals,
>fixed repayment loans (for which the function provided in 
>the loan druid
>works just fine) and probably a half a dozen more wierd 
>combinations.
>This is before we include rounding/truncation differences 
>and other
>oddities. The druid is not ever going to be able to cope 
>with all this
>reliably.

Right, but it shouldn't be that hard to work out three or 
four most common situations and have the Loan Druid ask 
which one applies, or have an option for "none of the 
above" where the user supplies an alternate calculation. 
Also, when you say that there are fixed repayment loans 
for which the function in the current Druid works - do 
those loans not allow extra principal to be paid? If they 
do, as soon as you pay extra the remaining payments will 
be wrong. This is why I would think that almost any loan 
is going to require the calculation to be based on the 
current loan balance.


>And once again, I'll point out that even with all this, 
>there will still
>be a need to check the results against your statements, 
>because of the
>rounding/truncation issues and whatever other magic the 
>banks perform in
>these calculations. The numbers should be right to within 
>a reasonable
>margin, but they may not be exact.

Right, in some cases there will be a couple cents 
difference between the bank's calculation. Particularly 
for a car loan, where the best a user can do is figure 
interest based on the day they write the check, and the 
bank will figure it based on the day they receive it. 
Still, that's no excuse for GnuCash to not be as accurate 
as possible. I'll also point out that some loans, at least 
in the U.S., don't provide monthly statements, just a 
"coupon book" of payments, so there's no way to 
double-check your amounts.