Level the retail playing field

[Commentary] It's an increasingly common sight at the mall: shoppers using their smartphones to scan the barcode of an item they like and checking its price online.

Some scanning applications go further, letting shoppers buy the item from a competing Web retailer with just a few taps on the screen. The largest online seller, Amazon.com, even offers customers up to $5 off the items they scan in other companies' stores. The brick-and-mortar shops may be able to match their online rivals' discounts, but there's one competitive disadvantage they can't overcome: Many online retailers do not collect sales taxes from customers outside of the state where they are headquartered. It's a problem for local retailers and governments that Congress has shown little interest in solving. But there are reasons to hope that the situation is changing. Good tax policy requires equal treatment of similarly situated taxpayers.