Evan Schuman's StorefrontBacktalk

Online auctioneer eBay is leading the fight against a proposed federal law allowing Internet sales taxes, and for very good reason: eBay, which currently collects no sales taxes, could find itself in the position of having to not only collect sales taxes for thousands of jurisdictions but spend a huge amount of effort closely tracking every auction to determine where buyers are located and whether sales tax is required on each item.

The “Main Street Fairness Act” introduced on July 29 would require conventional online retailers—including Amazon, which supports the bill—to collect sales taxes for states that meet the law’s requirements (24 states currently do). But exactly how the law would apply to non-traditional retailers like eBay isn’t so clear. That means Amazon could find itself no longer appealing a lawsuit in New York, launching a ballot measure in California and fighting “Amazon law” brushfires in other states—while eBay could face an IT nightmare.

The bill introduced last week by Senate majority whip Dick Durbin (D.-Ill.) would allow states that have signed onto the Streamlined Sales and Use Tax Agreement to require sales-tax collection by out-of-state online and mail-order retailers. The law would eliminate the requirement that an out-of-state retailer have “nexus” in the state—a store or an affiliate—before it has to collect sales tax.

That would effectively eliminate the need for the “Amazon laws” already passed by a handful of states, including New York, Illinois and California. It would also mean E-tailers that have affiliate marketing programs, including Amazon and Overstock.com, would no longer have a reason to kill those programs in an effort to dodge the sales-tax bullet.

Amazon, the online retailer that probably has the most to gain from killing those state laws, doesn’t think collecting sales tax for 45 states will be a problem. “We already collect sales tax or equivalent to more than half of our business or approximately half of our business across the world,” Amazon CFO Thomas Szkutak said in an earnings call on July 26. “We support a federal simplified approach, as we have more than 10 years.”

What Szkutak didn’t say is that a federal law would effectively end most of Amazon’s sales-tax-related legal fights. Those lawsuits involve efforts by states to define Amazon and other E-tailers as local businesses if they have affiliate marketing programs. Those efforts, in turn, stem from a 1992 U.S. Supreme Court decision called Quill v. North Dakota, which set limits on when a state could collect taxes through out-of-state retailers. A federal law would throw out the Quill standards, and with them Amazon’s current lawsuits.

Overstock.com, which is also involved in many of the Amazon lawsuits, would get that benefit, too. But Overstock still doesn’t like the proposed law. “We don’t think it’s fair to require companies that have no physical presence in a state to have to collect sales tax,” said Overstock President Jonathan Johnson. “We’re not using the local services, participating in the community or receiving the benefits of the sales taxes we’re required to collect.”

Johnson added that sales-tax collection “creates a barrier to entry for new businesses that will be insurmountable. Had we had to figure out how to collect and remit sales taxes in 8,000 to 15,000 jurisdictions, we couldn’t have done it and we would have gotten in trouble.” He said Overstock implemented a sales-tax system over the past year, and it took IT staff months to get it working right.

But it’s eBay that faces the biggest potential complications from Internet sales taxes—and the biggest IT investment.