Ex-Russian here: this year I had very pleasant experience with FNS to declare and pay income tax for some extra income (13% flat rate btw). 5 minutes on the web

Ex-Russian here: this year I had very pleasant experience with FNS to declare and pay income tax for some extra income (13% flat rate btw). 5 minutes on the web site just to declare the money they were not yet aware of, click submit and choose payment method (could be cash payment in any bank, credit card or via integration with lots of banking APIs - my choice). Few more minutes after I figured out there's a small old debt on property tax, that they never bothered to collect, to pay it too. They started with rather complex desktop app and continuously improved UX, so now it's really good. Worth to mention that they have 2FA option with security token.