It seems like a well thought-out proposal. I think I saw a survey at one point where 95% of economists agreed that if you want to disincentivize a behavior, tax it. Yet, this isn't a tax because it comes back to taxpayers. Even better.
“Minus administrative fees”.
I don’t trust our government to not fuck it up. How long before grift and general fuckery means the administrative fees are more than the rebate? You think the government is going to handle that much money going through their grimey little fingers without taking an ever-bigger piece of the pie, Social Security style? Nah.
The government already manages about a hundred tax breaks and various credits simply by adding lines and formulas to tax forms. I imagine the nuts and bolts of administering this would be no different, and it's a relatively simple way to reallocate incentives, even if the sum of all these tweaks adds up to very complex tax forms.
The people who lose are those who fail to file taxes - e.g. the very poor, the disorganized, the mentally ill or incarcerated, teenagers, hospitalized people, low-IQ individuals, the elderly in nursing homes, people who move and have paper checks mailed to old addresses, etc. So I'm less worried about government incompetence than I am about individual incompetence. People already leave billions of dollars in tax refunds on the table by not filing. It's the price of illiteracy or living in chaos.