Given that 'its the law' to pay tax, are we required to pay it ethically? Well, the answer is self-righteously No! Ethics is based on arguments of logic. The political system subjugates any individuals judgement on the matter, right or wrong, to the will of the majority, right or wrong. So arguments of logic are not the standard of value in politics.
So what role should logic play?
Well I have yet to see a legislator make a rational case for taxation, so they are likely to downplay the role of logic in favour of the common good, the will of society, and other collectivist terminology. They will of course be acting in their best interests, as opposed to what is good for society.
Should one accept the rational argument or live by the law?
That is a personal decision because clearly you might feel good saving money, but there are other taxpayers who would feel betrayed by your indifference to their cause. Their greater concern however is likely to be:
1. Their tax bill is bigger because you dont which to support services that they feel compelled to support, even if they didnt approve of them.
2. They fear government retribution so are unlikely to come to your defence
If you are in any doubt about the morality of taxation consider the following question - By what moral right can one person, or person claiming to represent any number of other people, seek to force another to pay taxation. Expropriation is robbery. The tax act is contrary to the principles of Common Law that extend back far greater than taxation. Taxation, as conceived in the UK, was a voluntary tax to defend rights. It was only dispotic monarchs that used the proceeds for their only political ends, and so it was for government when they ultimately sought to do the same thing. How is taxation different from any other crime? Its legitimatised theft.