Apparently you did not understand technically what
I proposed upthread. We can in theory anonymously (in zero knowledge proofs) prove the tax reporting period totals on our inputs and outputs from transactions we've participated in (but apparently not with Monero's current technology).
While taxes can be assessed and appropriate payment proven, payment of taxes cannot be forced in a decentralized currency that is not controlled by the government. The government can know that person 352 owes x dollars in taxes, but if he doesn't pay it and is anonymous, how can the government do anything about it?
The government cannot prevent anonymous currencies from being used, although it can sanction use of a cryptocurrency. This leaves the possibility of a large underground economy. One possibility is that taxation shifts from income-based to residency-based.
You misunderstood the point I was making, which is that in order to not incriminate yourself (i.e. compliant with laws that require you to report) and not have a risk of being caught, then you'd want a way to declare/report, but still maintain your anonymity (privacy).
Of course those who don't care about being illegal, will not declare/report, and I wasn't speaking about them. I presume the governments will track them down, because anonymity isn't perfect (the NSA can deanonymize you if they really want to).
Of course it is possible the governments (especially in the West) might go totally bezerk and make everything illegal (even breathing), in which case we'd use anonymity and not report and be in MadMax type collapse scenario (where even gold is useless and only food, guns, and hacking ability are money). In that case, we'll have bigger problems than crypto can solve, such as keeping the electricity turned on.