Tax laws need to be much, much simpler. The more complicated they are, the easier it will be for people to sneak by without paying and for loopholes to exist. It's the same thing that happens when a program drifts away from triviality - the probability of bugs increases greatly. Make tax laws trivial, and most of these problems - and most of the need for the IRS - would go away.
Tax laws generally start out simple, then get complex patching holes. My favorite example. Once upon a time a long time ago, a company wanted to pay a dividend to shareholders. That would be taxed as ordinary income to the shareholders. The company's accountants had a brilliant idea. 1. Do a stock split. Say, 105 for 100. 2. Do a stock buyback, where the company buys back 1/21 of the outstanding shares. Net result to…
If it's to stop Grandma getting hit with a huge marginal tax when she sells her house (despite it being a once-off kind of thing), just introduce some kind of smoothing. If your income is uneven, the tax man can give concessions (if you get a lot of money after a period of low income), and rebates (if you have a low income period after making a lot of money).
Easy, right? No more need for tricky rules about how to move money between the different categories.