Retailers are hoping for a resolution this year from the Supreme Court, which hears arguments Tuesday in a decades-old dispute: Whether companies must collect sales tax on items sold in a state where they don't have a store or other building.

If the court backs government officials who say they're losing billions of dollars in uncollected taxes, thousands of small companies could be forced to start charging their out-of-state customers for them. Some businesses fear that could alienate customers used to tax-free shopping. On the other side: Retailers who do collect sales tax and believe those who don't have an unfair advantage.

The justices will hear online retailers Wayfair, Overstock.com and Newegg challenging a South Dakota law enacted last May requiring out-of-state retailers that have sales of more than $100,000 or over 200 transactions a year in the state to collect sales tax. Their decision could have national implications on e-commerce, although Congress can pass legislation afterward that broadens or narrows the law.

It's not only about the money, says Stephanie Harvey, owner of exit343design in Conshohocken, Pennsylvania. There are more than 10,000 sales tax jurisdictions in the United States: 35 states, the District of Columbia, counties and municipalities.

"Adding this sales tax isn't just about the tax itself — it's about the cost of time to navigate and file (taxes) or the additional expense of hiring someone to do so on behalf of the business," says Harvey, whose design and printing company has an online store and sells merchandise to other retailers.

The justices are likely to rule by June on whether to overturn a 1992 decision, Quill v. North Dakota, that said companies cannot be forced to collect sales tax from customers in a state where they don't have a physical presence like a store or distribution center. Collecting tax from online sales hasn't been a question for big online retailers like Walmart or Macy's since they have physical stores in most or all states. They also have accounting systems and financial staffs to handle the work.

Small retailers have software options to help collect taxes and do the administrative work, but it's an added cost. Whether it's worth it may depend on how much revenue a seller gets from other states. The most comprehensive software can work with the programs retailers use to process sales transactions. The software sellers determine the correct sales tax rate and submit payments and reports to tax authorities.