One who makes a positive claim has to justify it. One cannot demand an argument against a positive claim from the skeptic. This not how reasoning works. For example, assume a friend of yours comes over to you and tells you, "I was abducted by aliens yesterday". You tell your friend, "I do not believe you". He tells you, "can you show that I am wrong?". Do you see what you friend did? He shifted his responsibility of defending his claim to you, he shifting from defending a claim to denying a claim. A claim does not need to be denied if there is no argument in support of it. Thus, if you friend is to ask you, "can you show that I am wrong?" all you have to say, "it is not my responsibility to show you are wrong, you are the one that needs to defend the claim". Likewise, I cannot be asked as a skeptic by a Jewish believer, "why do you not believe in Judaism?". Because Judaism is a positive claim. The believer who claims Judaism needs to supply the argument in defense of Judaism. Then and only then do I respond back to his defense and say whether it is a good defense or not. This is the correct way we need to think with regard to claims that people make, we need to demand their justification, if no justification is provided we may just ignore the claim.
The same attitude as above needs to be taken with regard to moral questions. It is not my responsibility to say why cheating on taxes is fine. It is the responsibility of the one who says that cheating on taxes is wrong to supply an argument. Consider this example. I do not have to ask myself, "is it okay to put on my right shoe before my left shoe?". Because, just like with undefended claims, I can do anything that I want if there is no defensible objection to it. If someone is to come along and say, "putting on your right shoe before your left shoe is morally wrong" then I will just ignore the person. I will not try to defend why putting on a right shoe before a left shoe is fine to do. Since the person who said putting on my right shoe before my left shoe is morally wrong and he did not justify his argument I can ignore his statement. Therefore, I demand an argument from one who says cheating on taxes is wrong. It is not my responsibility to say why it is okay. But if one who made the claim that it is morally wrong and gave a defense of his claim then it would be my responsibility to refute his defense or acknowledge he was correct.
It follows from what was demonstrated above that one who says, "cheating on taxes is wrong" needs to defend that statement. Let us look at the most common 'defense'. It is wrong to cheat on taxes because you are stealing money from the government. This moral argument says that it is wrong to take what is not ours away from other people and since this is what tax evasion does it follows that tax evasion must be morally wrong. There is just one huge problem with this argument. The money is yours! Taxation takes away the money that the citizen has earned, not the other way around, the citizen takes no money from the government, it is rather the government that takes money from the citizen. This defense of why tax evasion is wrong is a failed defense. So the defender of why tax evasion is wrong would have to try around to defend his moral claim.
Perhaps, the defender of this claim can use the following argument. Is it wrong to cheat on paying your bills? I agree that it is wrong to cheat on your bills. Why? I cannot use the argument that, "I am stealing money from the company", because against it is my money. It is wrong for a different reason. The company provided me with a service, I agreed to pay for their service, they provided me with a service, but I did not pay, I did not carry out my side of the contract. So I lied to the company. The company did something for me but I did not return them the favor. This is why it is wrong. Therefore, the defender of the claim that tax evasion is wrong can try using the following defense, "tax evasion is wrong because you need to pay back the government for what they did to you."
This is definitely a stronger defense of the claim than the first failed attempt, "you are stealing money from government". But this defense is still a failed attempt. Consider that you never use the government service. You simply do not want to use them. Then this defense is no longer applicable. One can no longer say, "you need to pay back for what they did to you" because it is no longer applicable, you never used them for anything. I agree that it would be wrong if a person is aided in his life by the government, past or present, and then decides not to pay for its help. However, I am talking about a person who does not rely on the government, rather relies on private enterprise or himself or whatever other external subject. We need to understand that we are taking about income taxes. Income taxes are taken away from a person for the income he earns for himself, the government comes and takes away a portion of his income. If this person is not associated with the government then the person can deny payment of his taxes, in this case it would be fine to cheat on taxes. Now there are other forms of taxes. There are local taxes. The local area in where this person lives has roads, police, fire department and other services, since he uses these services it would be wrong for him not to pay his local taxes (unless he really is an outcast and never uses anything), however, it is not necessarily wrong for him to pay income taxes because he may be disassociated from the federal government.
The defender of why it is wrong to cheat on taxes may use one more argument after seeing why his first and second defenses were failed defenses. He may say, "being a citizen comes with certain protections, like having a military to defend the country, so people need to pay for these protections and safeties". There is a problem with this argument. Consider this example. Say you have a neighbor who has a lot of private security guards. You are certainly more safe as a result of extra security. Can your neighbor demand money from you because his own protection benefits you also? No, he cannot. Because there is a difference between "direct benefit" and "indirect benefit". Direct benefit is the benefit derived purposely for the person, the neighbor has direct benefit from the security guards because he purchased them for that purpose, you, however, have indirect benefit, you do benefit from his security but only because its benefit extends into your zone. Repayment can only be demanded in the case of direct benefit. Therefore, even though it may be true that a non-taxpayer receives indirect benefit by being a citizen his income cannot be demanded by the government for that reason alone.
Back here I wrote about the difference between what is legal and what is moral. I happen to believe that if you are not satisfied with the way tax money is being spend by the government then you should be civilly disobedient and not pay your taxes (of course that would also mean to disassociate yourself from the government and not rely on their aid). I am opposed to the war. I think it is a great injustice the United States preforms everyday. Therefore, I do not have to give them my money, I do not have to support them, and I do not have to support what I think is evil. So the answer to my question, "is it wrong to cheat on taxes?" is "no" (though it would be wrong it you cheat but rely on government help at the same time).