Wouldn’t need an IRS if it was a flat tax.
Nor as many accountants and lawyers.
So, it ain't gonna happen.
Unfortunately we would. I hate to hear myself acknowledge that, but there will always be tax cheats.
I think the secret would be to severely limit their ability to accuse a person and seize homes, businesses, bank accounts without a warrant issued by a judge.
No more guilty until you prove yourself innocent.
The estate and gift tax is basically a flat tax and it keeps attorneys and cpas very busy with the IRS. A flat tax would increase the volume of similar issues that all taxpayers would use to avoid or reduce the flat tax.
As long as you're taxing someone then you'll always need an organization to process the returns. It may be smaller but it'll be there.