[libreplanet-discuss] free and libre tax software

[Greg Knittl]

Hi,

I'm interested in writing free and libre income tax software for Canada. 
https://libreplanet.org/wiki/Group:LibrePlanet_Ontario/FLCTPSP

Technically it's a challenge because of the shear quantity of 
calculations. It has to be easy for different people to add and maintain 
different pieces of the calculations because there's no chance I can do 
it all. This all has to mesh together somehow. It would be nice if 
accountants would pick it up and maintain it so the calculation engine 
and the data need to be well separated.

Each field requires a description in English and French, a formula, form 
name, line number, identifier number. It might also include references 
to the Income Tax Act. Formulae for a field can change depending on the 
context so the formula language may need to conditional expressions. 
This is probably more than a text file. Maybe a database, xml, json... 
just to contain the relevant information.

The calculation engine has to resolve dependencies and process the 
formulae. It needs to have minimal dependencies so it lasts. It could be 
written in C, but there is already tsort and bc. Bash could calculate 
dependencies by replacing variables with shell functions. Libre Office 
Calc resolves dependencies and processes formulae but how to input the 
formulae and other data in an automated way?

There needs to be output in a variety of formats: human readable, for 
electronic submission, suitable for difference operations (comparing 
against previous years or previous versions to create adjustments)

There are political obstacles that are probably more unique to Canada 
but it wouldn't surprise me if the Canada Revenue Agency (CRA) will 
argue that they don't want to expose the electronic tax submission 
interface for security reasons.

Are there any other free/libre tax calculation engines out there? I 
would think the technical challenges are going to be similar around the 
world. There may be similar political challenges to getting tax 
authorities to open up their interfaces. It would be very helpful to 
have examples of other countries where people do use free/libre tax 
software to submit their returns electronically.

thanks,

Greg