It has been indicated in a previous chapter that a customary part of early fiscal systems was to levy duties upon goods when they crossed a political boundary. They were called the " customary duties," and later simply customs duties. In modern times they are usually called tariff duties, and much is said and written on the tariff rather than on customs duties.
Only those duties upon goods which cross a national boundary line, or the line of some customs territory which is a part of a nation or combination of nations, are considered as customs duties. Duties which might be levied by a city upon goods, either coming in or going out over its boundary, would not come under this category. Neither would levies made upon goods going from one part of the country to another, as from one state or province to another, nor would those which might be placed upon goods passing through a country be classed as customs duties.
In the earlier development of these duties, levies upon goods going out of the countries were as important and significant as the ones upon goods coming in. Permission from the government to secure gain by trading with foreigners was considered a valuable privilege, and consequently a charge was made. Likewise it was considered perfectly proper to tax a foreigner who secured profits from trading with the citizens of another country.
As nations developed, however, the relative importance of these two classes of duties changed. The growth of the mercantilistic sentiment had much to do with the decline of duties on exports. Apparently one of the easiest ways to augment the growth of the money wealth of a country was to stimulate exports and retard imports, so duties were generally removed from exports. Frequently governments went further than this and gave bounties, in one form or another, upon goods which went to another country. The claim of mercantilism has lost much of its strength, yet duties on exports have not regained their early importance.
It should not be inferred that export duties find no place in modern fiscal systems. In comparatively recent years England used an export duty on coal, with the combined purpose of conserving the supply and raising revenue. Export duties still fill an important place in the fiscal systems of Turkey, India, and a few other countries, and are used upon a few products in some European countries. As a general rule, however, customs duties and import duties are practically synonymous in the programs of most important countries.