In most cases, tariffs and quotas harm consumers by causing

Unexpected deflation

Higher prices and fewer choices

Higher unemployment

Surpluses and waste

Higher prices and fewer choices.

Tariffs and quotas are protectionist trade barriers used by several countries to control import flows. Tariffs imply that importers must pay a tax for every unit of the good subject to the international tax. Quotas are restrictions in terms of the amount of certain goods that can actually get into one country as imported goods. Both measures can be implemented to protect local producers of certain goods. Examples of tariffs are those apply by USA to European agricultural goods, and examples of quotas are those imposed to China's textiles by USA (of course there are plenty of examples of this kind around the world).

Both tariffs and quotas decrease imports from other countries: the first one reduces imports because it makes them more expensive to importers, the second one reduces imports because it restricts the amount of goods that can be buy abroad.

Step-by-step explanation:

Quotas result in fewer choices because they directly restrict the amount of goods that can be bought abroad. Tariffs result in higher prices, because when they are applied, one must pay international price plus a tax.