The methods employed in underpaying or avoiding local, national and international assessments of various kinds correspond to the method of assessment. Most illegal acts in the private sector deal with concealment or under-valuation of assets, whether these be a farmer's crops, a corporation's income, or a private individual's inherited wealth. Other acts of avoidance apply to manufacturing, sales and usage taxes, and similarly are of the nature of non-declaration or understatement of quantities manufactured, sold, or used, and their worth. An industry for detecting avoidance exists, but it is almost entirely a government monopoly, administered by inland revenue or treasury offices. In some countries a reward is paid to private persons giving information on avoidance. Corruption in the form of bribe-taking by collectors or inspectors is a recurrent phenomenon.
The payment of duties is also circumvented in many ways, including illegal shipment or smuggling. The losses to local or national governments by tax subterfuges, illegal business, or recordkeeping, and by the various other methods of avoiding payment is significant, and as a result penalties are severe. Avoidance also hurts the private sector of the economy when taxes and duties relating to imports are circumvented, to the extent that such taxes and duties are protectionist and are designed to discourage a high level of importation of a commodity or product. Finally, governments which themselves may be taxed or proportionally assessed, for example, for their share of international costs of projects, or international organizational budgets, may also seek avoidance in the form of truant payments or defaults.