The issue of use tax in Arizona is divisive, as it typically refers to online retailers and their out-of-state sales. It can be almost impossible to keep track of all receipts, and record keeping is a nightmare. At present, there is a definite possibility of use tax being repealed at some point in the future, but for now, it places a huge burden on online purchasers.
In order to comply with state use tax regulations, you need to separate online sales where no tax was charged (such as sales on Amazon.com) from sales where tax was collected by the retailer (such as on Target.com). You also have to keep track of items purchased out of state and shipped into Arizona, plus out-of-state sales where there was no sales tax. Add in the fact that you also have to keep records of sales tax and most businesses are absolutely buried under the paperwork of record keeping.