Only if it's more efficient than the alternative. It may be that having special cases and extra complexity has a higher overhead than just getting everyone to

Only if it's more efficient than the alternative. It may be that having special cases and extra complexity has a higher overhead than just getting everyone to use the same path, even if that looks like "more" work from a distance. I dread to think how this may work if an individual has multiple income streams, some possibly for the public sector (so would be tax exempt), and how that may affect the total used to calculate tax brackets and similar. And the politics of defining that - no doubt whatever rules you use for this they'll be some situations that people consider unfair. It also makes it easier to compare income against the private sector, as each dollar income means exactly the same if both then go through the same tax system. The US tax system is already designed to put as much burden on the individual as possible (for whatever reason - possibly mostly lobbying from the industry that has grown up around this complexity) - more complexity feels pretty bad to me.