An excise is an indirect tax, meaning that the producer or seller who pays the tax to the government is expected to try to recover the tax by raising the price paid by the buyer (that is, to shift or pass on the tax). Excises are typically imposed in addition to another indirect tax such as a sales tax or VAT. In common terminology (but not necessarily in law) an excise is distinguished from a sales tax or VAT in three ways: (i) an excise typically applies to a narrower range of products; (ii) an excise is typically heavier, accounting for higher fractions (sometimes half or more) of the retail prices of the targeted products; and (iii) an excise is typically specific (so much per unit of measure; e.g. so many cents per gallon), whereas a sales tax or VAT is ad valorem, i.e. proportional to value (a percentage of the price in the case of a sales tax, or of value added in the case of a VAT).

Typical examples of excise duties are taxes on gasoline and other fuels, and taxes on tobacco and alcohol (sometimes referred to as sin tax)

Excise tax is notable for the vagueness of its definition. According to the New Oxford English Dictionary (Revised 2nd Ed., 2005), an excise is "a tax levied on certain goods and commodities produced or sold within a country and on licenses granted for certain activities" (emphasis added). The formula "produced or sold" is applicable to both domestic and foreign products. But the word "certain" is not further explained in the definition — or even in the etymology, according to which the word excise is derived from the Dutch accijns, which is presumed to come from the Latin accensare, meaning simply "to tax".

It would be impossible to give a general formula predicting which goods are subject to excise. Lists of such goods are readily provided by governments, and from each list one may be able to infer the motives for grouping such goods together; however, no explicit formula appears to be provided by any one government. For example:

In Australia, where the Constitution stipulates that only the Federal Parliament may impose duties of excise, the meaning of "excise" is not merely academic, but has been the subject of numerous court cases. Notwithstanding the terminology preferred by the Taxation Office, the High Court of Australia has repeatedly held that a tax can be an "excise" regardless of whether the taxed goods are of domestic or foreign origin; most recently, in Ha v New South Wales (1997), the majority of the Court endorsed the view that an excise is "an inland tax on a step in production, manufacture, sale or distribution of goods", and took a wide view of the kind of "step" which, if subject to a tax, would make the tax an excise. The fact that an "excise" need not discriminate between local and imported goods seems to imply that duties levied by Australian States on sales of livestock and registrations of new vehicles are duties of excise, while the wide view of the taxable "step" seems to imply that even the payroll taxes levied by the States are excises. Whatever the merits or demerits of such arguments, it is clear that the constitutional meaning of "excise" is wider than the everyday meaning.

In defence of excises on strong drink, Adam Smith wrote: "It has for some time past been the policy of Great Britain to discourage the consumption of spirituous liquors, on account of their supposed tendency to ruin the health and to corrupt the morals of the common people." Samuel Johnson was less flattering in his 1755 dictionary: "EXCI'SE. n.s. ... A hateful tax levied upon commodities, and adjudged not by the common judges of property, but wretches hired by those to whom excise is paid."

Deducing from the types of goods, services and areas listed as excisable by many governments, and considering the thinkers' comments, a logical conclusion might be that excise duty was originally invented for some or all of the following reasons:

As already mentioned, many US states tax drugs, partly in order to be able to impose heavier punishments, as the Kansas Department of Revenue states on its website:

There are at least two major criticisms of such legislation, however - see below.

Gambling licences are subject to excise in many countries; however, gambling itself was for a time also subject to taxation, in the form of stamp duty, whereby a revenue stamp had to be placed on the ace of spades in every pack of cards to demonstrate that the duty had been paid (hence the elaborate designs that evolved on this card in many packs as a result). Since stamp duty was originally only meant to be applied to documents (and cards were categorized as such), the fact that dice were also subject to stamp duty (and were in fact the only non-paper item listed under the 1765 Stamp Act) suggests that its implementation to cards and dice can be viewed as a type of excise duty on gambling.