Republican presidential hopeful and former Florida Gov. Jeb Bush. (Michael Loccisano/Getty Images)
Opinion writer

As others have pointed out, Jeb Bush’s tax plan axes taxes for pretty much everyone, but especially for really, really rich people.

Including, coincidentally, Jeb Bush.

The Republican presidential candidate would make out like a bandit under his own plan. According to my quick-and-dirty, back-of-the-envelope calculations based on Bush’s 2013 tax return, his liability for that year would have fallen by about $800,000, or about a quarter of what he paid Uncle Sam.

Here’s how I got that number. Bush’s adjusted gross income (A.G.I.) — all the money he received from wages, investments, etc., less the deductible part of his self-employment tax — was $7,274,764.

From that, he can subtract personal exemptions, for himself and his wife, totaling $8,000. Under the current system, he is considered too rich to take these exemptions, but his plan would allow him to do so.

Now we get to deductions. Here things get thornier.

Taxpayers have two choices: They can either take the standard deduction, a flat amount that doesn’t require any digging up of receipts; or they can itemize, which allows them to subtract specific costs such as unreimbursed work-related travel, mortgage interest, state taxes and medical expenses (subject to some restrictions and phase-outs for high-income people — more on that in a minute).

Bush would change a few things about how deductions work. He would raise the standard deduction, to $22,600 from the current $12,600 for married couples. For itemizers, he would eliminate the ability to deduct state and local taxes. Almost all other itemized deductions would stay, but taxpayers couldn’t deduct their full amounts; instead, their tax savings from deductions could add up to no more than 2 percent of their A.G.I.

Bush makes one big exception to this cap, however: charitable giving. Such donations wouldn’t be bound by that 2 percent limit.

So how would these changes have affected Bush?

He doesn’t actually have that much in itemized deductions. That’s because he has categorized his consulting and speaking income as part of his unincorporated business, “Jeb Bush & Associates.” This means he can call a lot of costs “business expenses” and subtract them from the income he reports from his company, rather than categorizing them as itemized deductions.

For example, Bush travels for work, and has some vehicle, legal and other miscellaneous professional services expenses. Regular employees can often count these unreimbursed costs as itemized deductions, but those numbers would be subject to the 2 percent cap; because Bush books the cost of that travel to his business instead (to the tune of several hundred thousand dollars), the cap wouldn’t apply.

He does have some personal itemized deductions, though. These include state and local taxes, mortgage interest payments and charitable donations. Altogether, he has over $200,000 in itemized deductions — but under the existing system, where we have a super complicated way of phasing out these deductions for rich people, the tax code only lets him “count” $56,980 of this amount on his 1040.

Under his plan, Bush could no longer deduct state and local taxes. Nothing happens to the treatment of his charitable giving. The rest of his itemized deductions, though, no longer get “phased out” as under current law, and they total $44,870. The amount of taxes that saves him doesn’t even come close to hitting that 2 percent cap. Including his charitable giving, his plan would let him deduct $155,486.

If you’re keeping score at home, that means Bush’s itemized deductions nearly triple under his plan compared with current law. They’re also way bigger than the standard deduction, so he’d almost definitely itemize.

Altogether, Bush’s taxable income — his A.G.I. minus exemptions and deductions — has been ground down to $7,111,278.

Here the real fun begins. Bush wants to lower tax rates, so that the top tax bracket for most personal income would be 28 percent (compared to 39.6 percent today), and that for investments would be 20 percent (compared to 23.8 percent for capital gains and dividends, and 39.6 percent for interest, under current law).

That means both his taxable income and the rate at which that income gets taxed would fall. Based on the amounts shown in his tax return for each source of income, he would pay $2,131,561. Before, he paid $2,920,698.

In other words, his tax plan — according these rough calculations — would put an additional $789,137 in his pocket, for a single tax filing year. Note that we haven’t even considered how much he might benefit from other changes he wants, such as killing the estate and gift taxes.

I’m not suggesting Bush wants to rig the tax system to reduce his own tax bill. But certainly he — like other very high-income people — would do very well by it.