Tax incidence is the effect a particular tax has on the two parties of a transaction; the producer that makes the good and the consumer that buys it. The burden of the tax is not dependent on whether the state collects the revenue from the producer or consumer, but on the price elasticity of supply and the price elasticity of demand. To understand how elasticities influence tax incidence, its important to consider the two extreme scenarios and how the tax burden is distributed between the two parties.
Inelastic supply, elastic demand
Because supply is inelastic, the firm will produce the same quantity no matter what the price. Because demand is elastic, the consumer is very sensitive to price. A small increase in price leads to a large drop in the quantity demanded. The imposition of the tax causes the market price to increase and the quantity demanded to decrease. Because consumption is elastic, the price consumers pay doesn't change very much. Because production is inelastic, the amount sold changes significantly. The producer is unable to pass the tax onto the consumer and the tax incidence falls on the producer .
Tax Incidence of Producer
When supply is inelastic but demand is elastic, the majority of the tax is paid for by the consumer. Since quantity demanded drops significantly in this scenario, the producer is forced to sell less.
Elastic supply, inelastic demand
Consumption is inelastic, so the consumer will consume the same quantity no matter the price. The producer will be able to produce the same amount of the good, but will be able to increase the price by the amount of the tax. As a result, the entirety of the tax will be borne by the consumer.
Similarly elastic supply and demand
Generally consumers and producers are neither perfectly elastic or inelastic, so the tax burden is shared between the two parties in varying proportions. If one party is comparatively more inelastic than the other, they will pay the majority of the tax.
Increasing tax
If the government increases the tax on a good, that shifts the supply curve to the left, the consumer price increases, and sellers' price decreases. A tax increase does not affect the demand curve, nor does it make supply or demand more or less elastic. This potential increase in tax could be called marginal, because it is a tax in addition to existing levies.