http://www.nolo.com/legal-encyclopedia/ohio-internet-sales-tax.html

The current default rule throughout the United States is that you must collect sales tax on Internet sales to customers in those states where your business has a physical presence. The physical presence rule is based on a 1992 United States Supreme Court decisionQuill Corp. v. North Dakota, that addressed the obligations of mail order businesses to collect sales tax on out-of-state sales; the decision has been extended to include online retailers. Generally speaking, a physical presence means having:

  • a warehouse in the state
  • a store in the state
  • an office in the state, or
  • a sales representative in the state.

The corollary to the physical presence rule is that, if you do not have a physical presence in the state, you generally are not required to collect sales tax for an Internet-based sale to someone in that state.