tax software (was Re:Speech on Linux...)

[Henry Spencer]

On Thu, 12 Aug 2004, James Knott wrote:
> I wonder if it's possible to create a standard app that could be used 
> every year, by reading in a new set of rules for that year's taxes. 

I wouldn't be at all surprised if parts of the commercial tax packages
already work that way.  But this doesn't really fix the problem, just
moves it:  now you need concentrated expert attention to revise the rule
set each year.  The hard part is understanding the changes to the law and
their implications, not embodying that knowledge in code.

> ...If that were possible, then Rev Can could provide the rules 
> that any tax app could use.

Unfortunately, I think this amounts to asking Rev Can to provide a tax
app.  There's so much complexity and so little pattern in it that to do
the whole thing, I think you'd need a program, not just a set of rules. 
I doubt you could write a rule-interpreting engine that could do the job
and wasn't essentially an interpreter for a programming language.

(Say you've got things running great, including the complications of
self-employment... and then RevCan decides that most small businesses
henceforth have to use the calendar year as their fiscal year.  That
actually simplifies things, but there's the problem of the transition:
to avoid forcing existing small businesses to pay two years of taxes in
one year -- which would wipe many of them out -- there's a complicated
procedure for spreading the income of the transition partial fiscal year
out over the next ten years.  Try to imagine a rule engine which can cope
with that and *isn't* a general-purpose interpreter.  This is a real
example -- that actually happened -- and this sort of weird complication
gets added fairly regularly.)

                                                          Henry Spencer
                                                       henry-lqW1N6Cllo0sV2N9l4h3zg at public.gmane.org

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