Several years overdue, legislation is moving through Congress that would allow states to collect sales tax on people making online purchases.

There are two powerful and undeniable reasons for the legislation to become law. First, leveling the playing field between online retailers and brick-and-mortar stores regarding the sales tax loophole is long overdue. Beyond that, closing the sales tax loophole will let states receive billions of dollars in sales tax revenue that they currently lose to online sales every year.

In the U.S. Senate, a bill called the Marketplace Fairness Act, introduced by Sen. Mike Enzi, R-Wyo., would allow states to collect sales tax from online sales, but would also exempt online companies with sales of less than $1 million. That bill is expected to be passed by the Senate, but the prospects in the House of Representatives are less clear.

A decade or so ago, when Internet commerce was just getting started, the argument against collecting sales tax was that it would hurt the emerging businesses. But online sales are no longer an emerging business. Retail giants Amazon.com and eBay dominate Internet commerce.

The amount of sales tax tied to online sales is estimated to be between $22 billion and $24 billion. With most state legislatures struggling with tight budgets, the additional money is desperately needed. And it’s not new money, or a new tax, as opponents to the bill suggest. It’s tax that has gone uncollected due to a loophole.

The loophole was created by a 1992 Supreme Court ruling having to do with catalog sales in which the court ruled sales tax did not have to be collected if the company did not have a physical presence in the state where the sales took place.

In addition to bringing states badly needed revenue, the issue is about fairness. For years, stores on Main Street or at the mall have been at a competitive disadvantage because they were required to charge sales tax, while a competitor, selling over the Internet, did not have to add sales tax to the purchase price.

Some online retailers complain about the burden of collecting sales tax, particularly when it comes to the complexity of sales tax, which varies from state to state and within some states, depending on the product sold. That concern is legitimate — and it’s addressed in the Senate bill, which requires that states provide software to help smaller online retailers apply the correct sales tax rate.

Elimination of the sales tax loophole for online sales should have been done years ago. Online retailers have had an unfair advantage for too many years. Now that reasonable legislation is finally moving through Congress, it’s time to level the playing field between brick-and-mortar stores and online retailers.

It’s about fairness and helping states receive the sales tax revenue that they should have been able to collect all along.

The Senate bill has strong bi-partisan support. It deserves the same broad support in the House.