It’s a decade overdue, but starting this month, Ama- zon.com will collect sales tax on purchases made by Pennsylvanians through the online retail giant’s website.

After years of fiercely fighting sales-tax collection, which regular bricks-and-mortar stores must collect, Amazon has agreed to start collecting the tax — and turning it over to the state.

The issue of sales-tax collection for online retailers has been debated for years. Online retailers pointed to a 1992 Supreme Court case that said only companies with a physical presence in a state were obligated to collect sales tax. That case involved catalog sales companies, since Internet sales did not exist at the time, but the online retailers made the same argument.

There have been two big issues in the sales-tax debate — fairness and the impact of lost tax revenue on state budgets. Letting online retailers avoid charging sales tax put stores located in malls or on Main Street at a price disadvantage. It was never fair that a customer buying a CD or a book at the mall had to pay state sales tax, but that same person could buy the same CD or book from Amazon or some other Internet retailer and avoid the sales tax.

In recent years, the issue of lost revenue has grown larger as most states have been struggling with budget deficits. The sales-tax loophole is estimated to have been costing states and cities that charge sales tax about $23 billion a year. Some reports suggest Pennsylvania is missing out on $250 million to $400 million a year in sales-tax revenue because of the loophole.

Amazon’s move will start to bring in some of that lost tax revenue. While Amazon is the dominant online retailer, there are many others. The existing rules have required larger traditional retailers, like Wal-Mart, Target and Best Buy, which have brick-and-mortar stores in the state, to charge sales tax on purchases made through their websites.

Last year, Pennsylvania made an attempt to collect the missing sales-tax revenue with an honor system approach, warning tax filers that they should divulge their online purchases and provide the appropriate tax. With Amazon’s move, the state has something better than the honor system.

Still, the best solution is not a state-by-state agreement, like the one Amazon has with Pennsylvania and six other states. The best solution is legislation from Congress that will set a national standard closing the Internet sales-tax loophole.

To be fair, imposing a national law for collection of sales taxes on Internet purchases is not easy because many states have confusing and often complex rules about what is, or is not, subject to sales tax. To address that, a cooperative effort, called the Streamlined Sales Tax Project, was begun in 2000. That project has made some progress simplifying sales tax rules — and 25 of the 45 states that charge sales tax have signed on to the agreement. Simplification is important, because collecting sales taxes should not put an undue burden on Internet retailers that have to deal with rules in different states.

With Amazon now collecting sales tax in Pennsylvania and a handful of other states, this appears a good time for Congress to create a national solution.

The reasons are clear nad compelling. Brick-and-mortar stores should be treated fairly when it comes to sales tax collection — and state budgets need the billions of dollars lost every year to the sales-tax loophole.