Sales tax (in the United States, at least) is a tax that is applied to the purchase of certain goods and services by a consumer. For example, when you go to the local office supply store to purchase some envelopes, in most states, you will pay anywhere from 4 to 10% extra in sales tax. This extra tax is collected by the merchant, who must then send it on to the state on a regular basis.
A similar tax, called a use tax, is imposed on similar types of products and services, but is supposed to be sent to the state by the consumer (though this is typically hard to enforce.) This typically happens when you order items from another state.
Sales tax is calculated bases on the sale price and the sale tax rate for the location in which the sale takes place. This rate can be a function of multiple tax rates. For example, in many states, you can have a base sales tax rate for the entire state, plus local taxes on top of that. Local taxes can be very widespread, like a whole county, or extremely specific, like a city tax.
For example, as of spring 2011, the statewide sales tax for California is 8.25%. However, within San Bernadino County, there is an extra .5% tacked on for the county's Transportation Authority, bring the total rate there to 8.75%. In the city of Placerville, CA, there is a .25% additional tax (bringing the total rate to 8.5%) that only applies within the city limits.
As a business owner, you need to submit sales tax to the state for any sales made from business locations within that state. Currently, if you sell products to customers who live in other states, and you have no business locations in that state, you need not submit sales tax for sales in those other states.
Most business owners pass on the sales tax to the purchasing customer, charging them based on the purchase amount and the tax rate. However, merchants must still pay the sales tax, even if they don't pass on the cost to the buyer.
Remittance is when you actually send the collected sales tax on to the state. Even though sales tax can consist of both state and multiple local taxes, as a business owner, you simply send the amount into the state and they take care of dispersing the extra money to local entities.
Several states offer discounts to business owners who remit their sales tax in a timely fashion. Being a good and timely tax payer can actually pay!
Because sales tax is money that is usually collected from a customer and sent on the the state, it does not affect a business owner's profit and loss.
Outright makes sales tax tracking easier for small-business owners by automatically importing and categorizing online sales information, including money collected for sales tax, and providing an up-to-date summary of what you owe the state.