I was thinking about what the implications would be if everyone still has to pay the same amount of taxes as they do now. But for a portion of their taxes they can decide to give it to specific projects directly that in some way benefit society. For example parents could add more funding to their local school for additional services, construction projects and so on. Is there a name for such a system? Has this been tested and are there any studies about the results?
If people get a say on how their taxes are spent you'd probably just call that (direct) (economic) democracy, maybe a version of socialism. If they get a say on how their share of the taxes in particular are spend probably a variation of hyperindividualism and if unequally distributed probably something like a plutocracy.
But from how you describe it, it also sounds like a tax deduction, that is you paid money on necessary expenses that otherwise the state would need to cover or gifted to charity or whatnot and that can be subtracted from your taxable income. Though this is usually limited and doesn't include your entire taxes.