To answer the question, it is necessary to know what a loophole is. Beverly Bird, at the balance, makes an important point. She writes, “Ask five people what a tax loophole is and you’ll probably get five different answers.” To prove her point, consider the definitions that are provided by various sources.
Beverly Bird provides this explanation: “Is it a tax break? Well…sort of, but not necessarily in an obvious way. Does a loophole save taxpayers money? Almost always when they can use them and if they qualify. . . Technically, a tax loophole is a provision that drains money from the government.” I disagree. A tax break is not necessarily a loophole, and most tax breaks are not loopholes. Tax breaks reduce tax revenue, even if they are not loopholes.
Over at smartasset, the same definition pops up: “The basic definition of a tax loophole is a provision in the tax code that allows taxpayers to reduce their tax liability.” The writer adds, “Lots of benign deductions and credits do just that,” and suggests there are “bad loophole[s]” and “good loophole[s].” Again, I disagree, for the same reason.
The folks at Dictionary.com provide a similar definition but then add an important proviso: “A provision in the laws governing taxation that allows people to reduce their taxes. The term has the connotation of an unintentional omission or obscurity in the law that allows the reduction of tax liability to a point below that intended by the framers of the law.” I agree with the sense of this articulation, but the focus isn’t the impact on tax liability in and of itself.
At InvestingAnswers, a different definition is provided: “A loophole is an exception that allows a system to be circumvented or avoided. It usually refers to legal, taxation, or security strategies that are exploited for personal gain.” An example is provided which I think misses the point: “Loopholes are failures of a system to account for all conditions, variables, or exceptions. To illustrate a legal loophole, consider a local development law that requires even an unoccupied building to pay real estate taxes so long as it receives a certificate of completion. In order to avoid paying taxes, a builder may exploit this loophole and choose not to "complete" the building.” Usually, the imposition of real estate tax liability based on a certificate of completion reflects the fact that a certificate of completion opens the door, literally and figuratively, for people or businesses to occupy the building, thus adding to the public burdens, such as sewage treatment, that require public expenditures the real estate tax is designed to fund. By failing to obtain a certificate of completion, the builder shuts to door on occupancy, and thus postpones the need for the government in question to incur costs. Put another way, the provision is intended to apply as it is written, that is, the certificate of completion is the benchmark for application of the tax. Note that as a practical matter, the property is still subject to the tax to the extent of the value of the land.
Those responsible for the definition at USLegal get it right: “A tax loophole is an exploitation of a tax law which can reduce or eliminate the tax liabilities of the filer. It’s a technicality that makes it possible for the filer to circumvent a law's intent without violating its letter.”
So however one defines tax loophole, agreement exists that tax loopholes exist. Thus, I was surprised to read this response given to the question asked on Quora:
According to the IRS, there is no such thing as a loophole. I learned that from an IRS Agent who was on a talk show years ago. Laws are made to address certain items and not others. That is the law.There are several problems with this response. First, something said by an IRS agent on a talk show is not necessarily, and almost certainly is not, official IRS position, even aside from the possibility that what the IRS agent said or intended to say wasn’t what the listener heard or understood. If the IRS does not think loopholes exist, then how does one explain its use of the word in this IRS News Release? Second, to state that laws are “made to address certain items and not others” begs the question, as is indicated by the following tautological statement, “That is the law.” Third, the IRS knows nothing. It is an organization without a brain. True, I’m being picky with articulation. What probably was intended was “The people at the IRS know what is and what is not legal.” And my reaction is to laugh, because I, and many others, can provide examples of instances when a particular IRS employee, or several or more, were flat out wrong on a matter of tax law. Fourth, to claim that taking a personal exemption of business deduction is not a loophole is to avoid the issue. The issues isn’t whether a business deduction is a loophole. The issue is whether a business deduction intended or designed to encourage particular behavior becomes a loophole in the hands of someone who finds a way to use the flawed language of the deduction statute or regulation to bring within the deduction behavior that is beyond the scope of what is intended. Personal exemptions and business deductions are tax breaks. That alone is insufficient to make them tax loopholes.
The IRS knows what is and what is not legal. Taking a personal exemption is not a loophole. Taking a business deduction is not a loophole.
Some deductions are made available to get investments from individuals to go into certain areas where the U.S. Government wants more investment funds. Those are not loopholes.
Loopholes exist. They are, simply, unintended tax breaks. They are the result of rushed or careless legislative drafting, fertilized by the inability of legislatures to know, understand, and predict every possible looming attempt to twist the tax break into something more than what was intended. And to answer the original question, “Is it illegal to exploit legal loopholes in the U.S. tax system to avoid paying taxes?” the answer is no. If a legislature doesn’t want people to benefit from a particular tax break, it needs to improve the initial drafting and to respond quickly and effectively when a loophole pops up. Note that the question contains its own answer. Is it illegal to do something that is legal? Of course not.