Offer your thoughts or opinion on the input financial query or topic using your financial background.

Is sales tax for online purchases based on billing- or shipping address?
The technical answer is defined by the laws of state you live in but most (all?) states with a sales tax have some form of use tax. Where if you buy something in another state for use in your home state you are technically liable for sales tax on it regardless of whether the merchant charged you tax on it or not. I don't think many people actually pay the use taxes, and enforcement generally seems rare.