That's a good start.
Daily or hourly uploads aren't real-time though. Why not just be fully real-time? Would an overnight allow for catching errors?
Why an average within the basket? If you have a defined basket, then the sum would be enough. Did it go up or down and by what percentage, yes? Why do we want to rule out outliers? If we keep them, we're better reflecting everything, aren't we?
How difficult would it be to handle all transactions of an industrial and consumer-goods-and-services nature sans financial speculation?
How do we deal with speculation influencing commodity prices? Futures have been highly contaminated by market manipulators using high frequency trading and the machinations of quants on behalf of the hyper-greedy "investment" banksters. Don't we get rid of finance capitalism altogether?
As for taxation to work in real-time, we would need every account to be reduced by an equal percentage. This truly would be sharing the pain but also the gain. If productivity remains real as opposed to the hocus-pocus of the derivatives markets, then we'd have vastly more gain across-the-board than setbacks.
The government would be issuing currency directly into the economy via public works and other government spending. If the projects are productive streams, it would be a boon for everyone beyond the wildest imaginations of most people.
More to the point though is that this is why I initially asked about whether we need the system to be economy-wide. We need more than seller data for real-time. We need buyer and seller account access. It would be the public bank, the US Treasury, controlling the supply in real-time.
In addition, we need to consider the velocity of money in terms of productive gains and losses, don't we? We're most interested in price inflation. People sitting on money is different. Reducing the total amount even though it's not all circulating seems to be an area that would need refinement.
"...the government would not get away with modifying the code behind the scenes in order to give themselves more money, thus creating inflation." I believe that the issue is with where the money is spent as opposed to "more money" per se. The supply must be exactly pegged to real productivity desired (voted for at every level) or we won't see growth. We must drive for growth in real productivity, sustainable productivity, healing productivity and all with an eye to increasing the quality of life for everyone. This would be Economic Democracy.
"No software would need to be run on anyone's home computers or handheld devices." The only reason I was thinking about this was in anticipation of handling all transactions rather than a basket of goods (where so many factors change), including people doing garage sales, and such (certainly not as Big Brother though but rather the exact opposite for once).
I should think that quality of life versus the value of a dollar is the simplest expression. Innovation will garner great quality of life if done right, but the supply must grow to accommodate people's buying (really sharing in the bounty). This is where real productivity loops back in.
So, I'm hoping others and you will map the big picture with this overarching view in mind as the target.
What I envision would render tax returns, per se, moot.
"All the sales data minus the name of the seller would all be public and downloadable so that the public could check it for outliers or for manipulation attempts by corrupt businesses." If we can bring more economic democracy to business and make business subject to more daylight and if we can get society at-large to self-promote cooperation for the shared benefit of all, we will have gone a long way to reducing the mentality that seeks to corrupt.
Beware the "angry bankers." That's wise advice. Ultimately, I see no need for commercial banks if the economy is sufficiently democratized.