Bug 103181: not-monthly repayment schedules not supported in Mortgage/Loan Druid

Derek Atkins warlord at MIT.EDU
Tue Jan 14 11:15:36 EST 2014

alessandro basili <alessandro.basili at cern.ch> writes:

> Uhm, isn't a 'balance as of date' automatically calculated? Executing
> the past transactions would immediately lead you to how much you 'should
> have paid so far'. Am I missing something?

No, it is not.  The P/I splits assume you always pay the exact amount.
If you over-pay your principal the P/I splits do not reflect the lower
principal (and therefore different P/I split ratio).  E.g., if your
mortgage is $995 (P+I) and you pay $1000, you've paid down your
principal by $5 and therefore are paying interest on $5 less principal.
GnuCash does not know how to handle this, so over time your
auto-generated P/I splits get further and further from reality.

>> I've been told this would be complicated, but I toss it out with
>> hope...
> For the sake of discussion (and understanding), isn't a 'compounding
> frequency' field be needed at the very beginning of the calculation? The
> Financial Calculator has it, so I wonder why the Loan Assistant does not.

I don't think that would be required necessarily for handling principal

But the complication of the balance-as-of-date is more a UI issue, where
you want the user to be able to select the account and have the name
shown in the UI, but you want to store the Account GUID in the SX

Right now the SX editor doesn't do that, it's a direct string store<->display.

> Moreover it seems that the Loan Assistant allows to have a period of
> repayment which is different from the compounding one, fine, but should
> it be reasonable to give 'any' frequency? How reasonable it is to have a
> be-weekly compounding frequency and pay the mortgage every 23 days?

I think it is reasonable to limit it to all the 'reasonable'
frequencies.  I don't think "every 23 days" is a 'reasonable' frequency.


       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       warlord at MIT.EDU                        PGP key available

More information about the gnucash-devel mailing list