The avoidance of income tax is a practice that is common in tax systems across the whole world. As Jensen notes, '[n]othing is certain but death and taxes? Not true. If taxes are certain, then so too are tax avoidance, tax evasion, and governmental efforts to contain the avoidance and evasion'. Being an inevitable concomitant of tax, tax avoidance, if left unchecked, can result in the substantial erosion of tax bases. A common way of controlling tax avoidance is introducing legislation that regulates the limits of permissible tax avoidance and targets impermissible tax avoidance. This legislation comes in the form of general anti-avoidance rules (GAARs) or specific anti-avoidance rules. The term GAAR means that the rule is broad and is a weapon against all forms of impermissible tax avoidance, which differentiates it from specific anti-avoidance rules, which are only applicable to specific forms of impermissible tax avoidance. In countries such as the United States, the United Kingdom (up until July 2013 when a GAAR was introduced) and the Netherlands (where both a GAAR and judicial doctrines are in place), reliance is placed on judicially created doctrines against impermissible tax avoidance. These judicial anti-avoidance doctrines function as GAARs because they serve a general anti-avoidance purpose and apply to all forms of impermissible tax avoidance.