Israel recently adopted severe legislative measures against the "aggressive tax planning" used by taxpayers, especially following the transition from the "territorial" to the "personal" basis for imposing the income tax. The term "aggressive tax planning" has not been statutorily defined, but a commission appointed for dealing with aggressive tax planning has pointed out many of the characteristics that are common to it. To enable the Israeli Revenue to have more information about the tax planning techniques used by taxpayers, the legislature enacted detailed rules imposing the legal obligation to disclose information that will enable the Revenue to counteract any tax planning which it considers to be "illegitimate" tax avoidance. This article examines the new rules prescribing the information that taxpayers are now required to give. The article also surveys the general attitude of the Israeli courts towards tax avoidance.