Attention online shoppers: The days of tax-free shopping on the Internet may soon end for many of you.

The Senate is scheduled to vote Monday on a bill that would empower states to collect sales taxes for purchases made over the Internet. The measure is expected to pass because it has already survived three procedural votes. But it faces opposition in the House, where some Republicans regard it as a tax increase. A broad coalition of retailers is lobbying in favor of it.

Under current law, states can only require retailers to collect sales taxes if the store has a physical presence in the state.

That means big retailers with stores all over the country like Walmart, Best Buy and Target collect sales taxes when they sell goods over the Internet. But online retailers like eBay and Amazon don’t have to collect sales taxes, except in states where they have offices or distribution centers.