Most states have sales tax. This is not a federal tax, but a state and local one. It is attached to items sold by retailers of everything from clothes and food to cars. After being collected by retailers, the sales taxes are sent to the state government, which disburse any local portion back to county governments. Typically a form of some type is used to help figure the tax breakdown for a particular month or quarter and a number is assigned to each business so that records can be kept properly. This number is a sales tax number and must be used when turning in sales tax funds.
Look through your paperwork for a state government letter. Most states will send a registration acknowledgement letter to new businesses letting them know about their sales tax responsibilities after they have registered with the state for a sales and use tax permit. If you misplaced your number during registration, this letter has your sales tax number on it just under your business name and address.
Look on the forms you send in with your payment. States will send you a new booklet every year with your business information pre-printed on the forms. Your sales tax number is among the information printed.
Contact your state government. If you are a new business, you might not have a sales tax number or have not received any papers about it yet. In that case, call to find out your number or start the process for obtaining one. In most states you will need to get in touch with the revenue department to register for sales and use tax. The name of this department can vary widely from state to state. In some cases it is actually called the Department of Revenue such as in North Carolina or Tennessee. In other states like Texas it is referred to as the Texas Comptroller's office. If you haven't registered and been assigned a sales tax number, they will let you know what paperwork needs to be filled out in order to obtain one. In some cases the registration can be done online.