Image source: Hillary Clinton for President.

With about a month left in the 2016 Presidential election campaign, Donald Trump and Hillary Clinton have started to hammer home their stances on important policies. Few issues inspire more controversy than taxes, and the philosophical differences between Republicans and Democrats are quite clear in the tax policies their respective candidates have embraced.

Hillary Clinton says that she wants to make the U.S. tax system fairer, and she has identified several provisions of the tax code that she argues favor the wealthy at the expense of the middle class. Below, we'll look at three of the biggest tax loopholes that the Clinton plan aims to close.

1. Overseas corporate inversions

One of the most egregious practices among major companies in the past several years has been the corporate inversion. To do a corporate inversion, a U.S. company typically seeks to acquire a smaller company in another country that has lower corporate tax rates. The U.S. buyer then moves its tax home to the target company's country, reducing its tax bill. Yet the buyer typically retains the bulk of its operations within the U.S., only technically shifting its domicile for tax purposes.

Already, the federal government has clamped down on corporate inversions, with the Treasury Department issuing regulations aimed at prohibiting repeated inversions and requiring that the acquiring and target companies be relatively close to each other in size. The regulations effectively killed a planned merger between Pfizer (PFE) and Allergan (AGN), in part because Allergan had made several acquisitions subject to the regulations and in part because Pfizer was so much larger than Allergan.

Yet Clinton wants to take things a step further, charging an exit tax on corporations that move their tax homes from the U.S. to another country. That's similar to what the U.S. tax system does to individual expatriates who give up their personal citizenship in order to avoid tax, but businesses argue that the unusual way that the U.S. taxes corporations on worldwide income is the true culprit motivating inversions. Clinton believes that by ensuring that companies at least pay something on their foreign earnings, closing the loophole would be beneficial to the government and the American public.

2. The carried interest provision

The way that Wall Street professionals get compensated was an issue in the 2012 Presidential campaign, primarily because former Republican Presidential candidate Mitt Romney had experience in the financial world. The carried interest provision allows managers of hedge funds, private equity companies, and other investments to take their pay as a share of the profits from the investments they make. Because these performance fees are based on the behavior of the investments, the tax code taxes them as long-term capital gains at a maximum rate of 20%.

Clinton would tax carried interest as ordinary income, arguing that these fees are received as compensation for the investment management services that financial professionals provide. Opponents argue that unlike the portion of compensation that comes as a fixed percentage of assets under management, performance fees are speculative. With similar techniques available for employees who receive stock options under certain types of incentive plans, focusing on carried interest only singles out the financial community, while leaving other loopholes untouched.

3. Estate-tax valuation strategies

One area of taxation that continues to draw strong feelings is the estate tax. Opponents refer to the levy as a death tax and see it as double taxation of money that has already been subject to income tax, but Clinton believes that the tax serves a purpose and is aiming to strengthen it.

In particular, Clinton wants to close loopholes that give the wealthy an incentive to use strategies aimed solely at tax avoidance. One such strategy uses a particular type of trust known as a grantor retained annuity trust, or GRAT for short. By structuring trusts in a certain way, current law arguably allows donors to set up trusts that make a gift to heirs of a remainder interest that has a value of zero for gift-tax and estate-tax purposes. Yet often, what the heir receives is actually worth something, and that value effectively escapes estate taxation.

With exemption amounts of $5.45 million for 2016, few estates are subject to federal tax. However, those that are still have plenty of incentive to use loopholes like the zero-value GRAT, and Clinton would seek to make it and similar vehicles for estate-tax planning unavailable.

Hillary Clinton argues that her tax policies are aimed at making the tax system fairer. Whether you agree or disagree, it's likely that if she wins, Clinton will work hard to close these and other perceived loopholes in the current tax laws.