For a while a lot of non-aligned countries were mandating the exclusive use of open-source software by government agencies, because the idea of their government being beholden to a US corporation was anathema. I suspect this was the motivation behind eliminating the Microsoft-only government service.
I haven't heard much about that open-source requirement lately. I suspect the Long Reach has been making quiet moves behind the scenes, and the ascendancy of neofascist regimes in many of those countries will do what fascist regimes always do (ie. cater to the cartel making up the fasces).
In the Netherlands we had (for a very short while at least as far as I remember) a DOS program as well on diskette. I never used it but my dad did when internet explorer was not yet evil and msn was a network. You could send it in via modem (9k6 baud yay!) and it would work ... sometimes or hand it in via the diskette. Once the internet got going you could send it more easily as you could send the created files directly instead of relying on the modem dial-in via dos.
For myself I never filed on paper (2002 first one). After the introduction of windows programs they ported it to linux the next year (filed the first one on windows only on a library pc, program might have existed earlier) and have now switched to web based. If you had a company which did their taxes on time everything was (and is) filled out mostly correct. You check it and sign off. As a student it took a while to fill in all the deductibles but if you just have to pay you are done in minutes.
Is/was it perfect? Far from. Does it work for most people? Yes.
My cousin started work as a company messenger back in the early 80s and these are the sort of tasks he used to do. Its amazing that the profession has died out in in such relatively short space of time. I guess courier companies have filled in the slot but courier companies would never have coped with the number of documents that needed to be ferried about town in the old days.
It's been replaced by something far nicer and web based! Though the old application was still definitely better than doing taxes by hand or having to pay for some third-party thing.
Other fun stuff about that desktop app...
* Originally, it was a DOS-only program (yes, it's that old). Then for a while, it was Windows-only, then for some time (probably due to the Linux users complaining) there was both the Windows-only version and the Java multi-platform version, and later the Windows-only version was discontinued.
* The original way of sending the output of this program to Receita Federal was to write it to a floppy disk and take it to a bank, which would read and upload it. Later functionality was added to send it through the Internet instead, and some time later the floppy disk option was removed.