This weekend, the New York Times broke the story that Republican presidential nominee Donald Trump claimed a $916 million loss in 1995, possibly allowing him to avoid paying federal income taxes for as long as 18 years. The ability to use a large, one-time loss to reduce future income tax liability is not, on its face, all that objectionable—it simply allows individuals to smooth out their tax liability and avoid being penalized for having a volatile income.1 But Trump’s refusal to release his tax returns continues to obscure the numerous other potential loopholes that can be exploited by those at the top that are more arbitrary and objectionable.

Take one loophole that is especially relevant to Trump and real estate developers: “like-kind exchange.” Like-kind exchange allows investors owning real estate to defer, and coupled with another loophole in our tax code eventually avoid, paying capital gains taxes.

To see how, consider an investor who owns a stock and would like to invest in another stock. Selling their stock will trigger capital gains taxes. Not so for real estate. Instead, like-kind exchange rules allow investors like Trump to defer paying taxes on their capital gains if they’re exchanging the real estate for broadly defined like-kind property.

Now, let’s say Trump keeps using like-kind exchanges to avoid paying his capital gains taxes. When will these taxes be paid? Not at death—thanks to the stepped-up basis of capital gains. The “basis” is the original value of an asset. If an investor buys an asset for $1 million and sells it for $3 million, they are taxed at the capital gain of $2 million. However, if the asset is held until death, then the basis of the asset is “stepped up” to $3 million when it’s transferred to an heir. This loophole allows for capital gains taxes to be avoided entirely once the assets are transferred to Trump’s heirs.

The estate tax stands as the last line of defense against wealthy tax dodgers. So we shouldn’t be surprised to see that Trump plans to eliminate it. Trump’s plan would at least end the stepped up basis, but only for estates valued at more than $10 million. On the other hand, Hillary Clinton’s far more ambitious tax plan would both strengthen the estate tax and end the stepped up basis that allows capital gains to be avoided entirely by wealthy heirs.

Maybe Trump really did suffer a billion dollar loss that he’s perfectly justified in applying to future years’ tax liability. This doesn’t affect the fact that other aspects of the tax code have gaping, unjustifiable loopholes that high-income households can exploit. We really should start closing those.

1. To see this, think of a simple example with two individuals. One individual makes $100,000 a year, but takes deductible capital losses of $50,000 in both years. The other takes a capital loss of $100,000 the first year, but makes $200,000 in the second year. At a tax rate of 10 percent, the first individual pays $5,000 in taxes both years for a total tax bill of $10,000. For the second individual, they have no taxable income the first year and therefore face no income tax. However, in the second year they pay $20,000 in taxes. Without such a provision, the individual with the more volatile income faces a 100% higher tax bill solely due to the volatility of their income.