(2) The tax which each individual is bound to pay ought to be certain, and not arbitrary. The time of payment, the manner of payment, the quantity to be paid, ought all to be clear and plain. This is the #maxim of certainty#, and it is very important, because, if a tax is not certainly known, the tax-gatherers can oppress people, requiring more or less as they choose. In this case it is very probable that they will become corrupt, and will receive bribes to induce them to lower the tax. On this account duties ought never to be levied according to the value of goods, or _ad valorem_, as it is said. Wine, for instance, varies in value immensely according to its quality and reputation, but it is impossible for the custom-house officer to say exactly what this value is. If he takes the statement of the people who import the wine, they will be tempted to tell lies, and say that the value is less than it really is. And as it would not be easy to prove the guilt either of the customs officer or of the importers, it is to be feared that some officers will receive bribes. But if the wine is taxed simply according to its quantity, the amount of duty is known with great certainty, and fraud can easily be detected. The same remarks apply more or less to every kind of goods which varies much in quality.
(3) Every tax ought to be levied at the time, and in the manner, in which it is most likely to be convenient for the contributor to pay it. This is #the maxim of convenience#, and the reason for it is sufficiently obvious. As government only exists for the good of the people at large, of course it ought to give the people as little trouble as possible. And as the Government has immensely more money at its command than any private person, it ought to arrange so as to demand a tax when the taxpayer is likely to be able to pay it. Thus there seems to be no sufficient reason why the government should make people pay the income-tax in January, when they are likely to have plenty of other bills to pay. In respect of this maxim, the customs and excise duties are very good taxes, because a person pays duty whenever he buys a bottle of spirits or an ounce of tobacco. If he does not want to pay taxes, let him leave off drinking and smoking, which will probably be better for him in every way. At any rate, if he can afford to drink spirits and smoke tobacco, he can afford something for the expenses of government. The penny receipt duty, again, is in this respect a good tax, because when a person is receiving money he is sure to be able to spare one penny for the State, and he is generally so glad to get his money that he thinks nothing of the penny.
