@Azure Here in Belgium the tax administration already knows about my income as my employer had to let them know, so I just have to (electronically) sign the pre-filled paperwork using my ID card. I still would have to edit it before submission if the situation was less straightforward though (eg if I had kids, or owned a house that I rented, made tax-deductible donations, earned money abroad, ...) but that's a balance between convenience and privacy that I'm happy with.