Generally the sales tax of the seller will apply. If a buyer purchases and takes delivery outside the seller's jurisdiction then the seller's sales tax would not be applicable. But any sales tax in the jurisdiction where the purchaser took possesion may be applicable. The seller would usually only be required to collect sales tax where the buyer purchases and takes possession within the seller's jurisdiction. The responsibility would be on the buyer to self-assess and pay sales tax in the jurisdiction where the buyer took delivery or where the good or service will be used. A self-assessed tax would not be included on a purchase order or invoice but would simply be paid directly to the Buyer's governing body. The client should consult authorities in their jurisdiction to confirm the requirements for collecting sales tax especially where a transaction involves multiple jurisdictions. (e.g. where the seller is located in Kansas and is shipping to a buyer who takes possession in Florida, the Kansas sales tax would not be applicable but the buyer may be expected to self-assess in Florida)