In objectivism, taxation is taken to be a form of theft because of property rights and the threat of loss of liberty if one does not pay. However, when someone agrees to work in a country with income taxes, aren't they agreeing to be taxed? A person knows what the tax implications are when they take the job. If they don't want to be taxed, shouldn't they refuse to work where there is taxation? I know in the US some taxes are withheld and some are paid annually. It's not of essential importance to the question but let's assume that all taxes are withheld and there has been a constitutional amendment of some sort that would prevent Congress from changing the tax code so you know going in what percentage of your income is going to be withheld and can plan accordingly. This is obviously not theft, as theft would be taking what is already in one's possession or denying someone something that is legally entitled to them. It would also not be involuntary because you would have at least implicitly agreed to be taxed a certain amount when you agreed to the job. This type of argument (if you don't like it, don't agree to it) seems to be used very often by objectivists even when there is a discrepancy between the two parties in terms of wealth, power, positive liberty, etc. Why would it not also apply to the issue of taxation when a person agrees to work in a jurisdiction with income taxes? How are individual rights being infringed in this case?
Consider a hypothetical: You are in a society, doing your job, living free, with no taxation. Everything's great, as far as you care.
Then the government changes, enacting an income tax. Your take-home play goes down by about a third.
You try to find a job which doesn't require income-tax, but you cannot find one in your area.
In order to live, you have two choices: stay and pay, or leave (presuming you can find a place where you don't have to pay income tax).
This is case where you are being forced, by people, to do one of two things which you hadn't had to do before: pay, or leave. You are being forced by someone who uses guns and authority to back up his demands.
In a sense, if you leave, you are "agreeing" to leave. And if you stay, you are "agreeing" to pay the tax. But in either case, the "agreement" is under duress. Without the presence of the official's authority and guns, you would do neither thing. You'd just stay and work, happily. Now that income-tax has come to town, you must leave, or pay.
The income tax has been imposed upon you, by the threat of force. That you must comply, in some way (either leaving or paying) doesn't mean at all that you've agreed to comply.
Where force exists, consent does not.
The claim that one "agrees" to pay income tax by accepting a job would only be valid if other jobs were locally available which did not require income tax: "Hey, you accepted the taxed job, rather than the non-taxed job, so quit your complaining!"
Taxation is like Mafia protection money. "Pay us if you stay here, or some of your property will get damaged."
Of course, one might make the analogy with paying rent to a landlord, but that would be ignoring that neither the government, nor the Mafia, owns the land. In both cases, the offensive institution simply finds a place where people are too afraid to fight back against injustice. They effectively roll into town, draw their guns and rob people, and then make a repeating habit of it because they have enough guns to enforce their will on the victims.
What's more, if they are clever, they disarm their victims morally. They donate some of the blood-money to local charities and schools, and claim to be exercising virtue on behalf of the victims. This rationalizes the theft in the minds of the victims, adding the power of convention to the power of the guns.
Eventually the victims grow used to being victimized, and come to think of taxation as metaphysically necessary. This reverses their sense of morality: instead of being indignant at their victors, they become indignant at anyone who would refuse to pay the tax, calling them stingy or uncharitable.
This kind of moral reversal is the result of choosing to live under (or retreat from) force, rather than fighting to overthrow it.
If someone comes to your home, draws a gun on you and says "give me a third of your take-home pay or get out of town", it might make sense, short term, to give him some money to get him to holster the gun, but as soon as he does, it's very foolish to set up a long-term agreement with him to keep giving him money as long as he doesn't shoot you.
Unfortunately, many, many societies exist under such agreements. Their citizens have been both physically and morally disarmed. On the one hand, a victim can be blamed for not fighting the taxation. But on the other hand, for the citizens to band together and overthrow the government can represent a very serious and dangerous risk to their lives.
When you see a crime being committed, and you see that the victim has given up fighting for himself against the victor, you might have some contempt for the victim, but you should condemn the victor first.
Never say to the victim: "You aren't fighting back, so you have agreed to be harmed -- so there's no crime here."
Taxation is a crime. And taxpayers are battered, broken victims -- they are not willing, self-possessed parties in a civil transaction, even if they pretend they are by saying foolish things like "I'm willing to pay my taxes." They've been, in a very important sense, owned.