(a) A tax is a compulsory levy imposed by the government on individuals and firms.
(b)(i) Equity / Ability to Pay: It is fair to assume that those who have the greatest wealth or the highest in-come should pay higher. This implies that revenue should be raised without causing undue hardship to the tax payer.
(ii) The Revenue yield: From the standpoint of the government, the total revenue that tax yields is of considerable importance. Governments are comfortable with . taxes that provide a fairly predictable and steady in-come.
(iii) Economy: Consideration must be given to the cost of collecting a tax, since high cost incurred in administering a tax may make it uneconomical for both the tax payer and the government.
(iv) Neutrality: An important consideration in evaluating tax is how the tax affects production, savings and people's willingness to work. A good tax system should not interfere unnecessarily with the supply and demand for goods and services.

(v) Convenience: The method and time of payment should be convenient to the tax payers.
(vi) Benefits - Received principle: It is argued that those who benefit most from government supplied goods or services should pay the taxes necessary for their financing. For example petrol taxes are typically ear-marked for financing road construction and repairs. Toil gates. etc.
(vii)Certainty: Governments and the tax payers should know about the amount, time, method of tax payments with certainty.
(viii) Flexibility: The tax system should be flexible enough for adjustments when the need arises.
(ix) Simplicity: Taxation should not be difficult to administer and understand. It should not cause problems of differences in interpretation.