New Jersey's Sales and Use Tax Act is most often cited to refer to sales taxes while the use tax http://www.state.nj.us/treasury/taxation/pdf/pubs/sales/anj7.pdf tends to be less well known. When goods or services are purchased outside of the state for use in New Jersey, and the sales tax was not collected by the out of state retailer, or collected at a rate less than the New Jersey sales tax rate, then the use tax comes into play.
New Jersey recognizes the concept of reciprocity when considering the sales taxes of other states. This means that when goods or services are purchased and received in another state to be brought into and used in New Jersey, and sales tax is paid to that non-New Jersey state, New Jersey credits the purchaser for the taxes paid. However, New Jersey does not allow this credit unless there is a reciprocity agreement between the two states where both states recognize and honors the same reciprocity for each other.
If the tax rate in the state is equal to or greater than New Jersey's, no use tax is due. (New Jersey's current sales tax rate is 7 percent.) For example, if the non-New Jersey purchase was for $100 and the sale tax rate paid by the purchaser in that state was 5 percent, the purchase paid taxes in the amount of $5.00. Thus, the New Jersey use tax would be $2.00. If the non-New Jersey purchase taxed at a rate of 8 percent, no additional use tax would be due and owing to New Jersey.
If the out of state purchase is delivered directly to the purchaser in New Jersey, there is no credit for any sales tax paid to the other state. New Jersey's use tax is therefore due for the full 7 percent of the purchase price, including any delivery charges.