Tax avoidance is the legal utilization of the tax regime to one's own advantage, in order to reduce the amount of tax that is payable by means that are within the law. By contrast tax evasion is the general term for efforts to not pay taxes by illegal means. The term tax mitigation is a synonym for tax avoidance. Its original use was by tax advisors as an alternative to the pejorative term of tax avoidance. Latterly the term has also been used in the tax regulations of some jurisdictions to distinguish tax avoidance foreseen by the lawmakers from tax avoidance which exploits loopholes in the law.

Some of those attempting not to pay tax believe that they have discovered interpretations of the law that show that they are not subject to being taxed: these individuals and groups are sometimes called tax protesters. An unsuccessful tax protestor has been attempting openly to evade tax, while a successful one avoids tax. Tax resistance is the declared refusal to pay a tax for conscientious reasons (because the resister does not want to support the government or some of its activities). Tax resistors typically do not take the position that the tax laws are themselves illegal or do not apply to them (as tax protesters do) and they are more concerned with not paying for particular government policies that they oppose.