April 15, 2011
By law (in the United States) you are required to collect Sales Taxes on any online transaction that happens within the State you operate.
You are not required however to collect Sales Tax on purchases that happen from outside your State. For these kind of situations we suggest adding language to your CheckOut page about Sales Tax and how your online store collects this from applicable purchases.
Customers may still be responsible for paying Sales Tax to their respective State but you are not required to collect it from them during the transaction.
Some Shopping Carts allow you to add Sales Tax based on Zip Codes so you can make sure you are collecting the right percentage rate on each individual purchase.