While I suppose it depends on the proposal in question, the ones I've seen generally follow a "make the simple cases easier" rule: get the forms pre-filled with what's possible to prefill, verify what's filled in is correct, and if necessary, complete what's missing. If you need to file for deductions that such a system misses, it doesn't have to be any harder than it is now.
Think about how users interact with software and how often they adjust default settings. Any additional forms outside of the pre-filled forms will likely get ignored by a sizable amount of people. That's what I meant by an indirect tax hike.
