What Marketplace Facilitator Laws Mean for Multi-Channel Sellers

What Marketplace Facilitator Laws Mean for Multi-Channel Sellers

Amazon already collects sales tax on your orders. So you're done, right?

That's the assumption that lands sellers in front of an audit letter three years later. Marketplace facilitator laws explained in one sentence: the platform collects and remits the tax, but the platform is not you, and a few states still want to hear from you directly.

Here's what that actually means when you sell across more than one channel.

Marketplace facilitator laws, explained: what they actually do

After the Supreme Court decided South Dakota v. Wayfair in June 2018, states stopped needing a seller's physical presence to require sales tax. They just needed economic activity — a dollar or transaction threshold. That created a mess: thousands of small sellers suddenly owed tax in dozens of states.

States solved their own collection problem by pushing the work upstream. Marketplace facilitator laws make the platform — Amazon, Walmart, eBay, Etsy, TikTok Shop — responsible for calculating, collecting, and remitting sales tax on the sales it facilitates.

Every U.S. state that has a sales tax now has a marketplace facilitator law on the books. That's all 45 sales-tax states plus Washington, D.C. So for the orders that flow through a big marketplace, the tax is genuinely handled.

The catch is in the word "facilitated." It covers sales on the platform. It does not cover everything else you do.

Why "Amazon handles it" is only half true

The facilitator collects on its own transactions. Your obligations as the seller of record don't fully disappear — they shift.

In a lot of states, you still have to register for a sales tax permit if you've crossed economic nexus there, even when 100% of your sales in that state run through Amazon. And many of those states still expect a return.

That return is often a zero return or an informational filing: you report your gross marketplace sales, then deduct them as "tax collected by a marketplace facilitator," and the bottom line shows $0 owed. The tax is paid. The state still wants the paperwork that proves the facilitator paid it.

Here's the pattern that bites people: the rule varies by state. Some states explicitly excuse a marketplace-only seller from registering. Others don't. Treating all 50 the same — in either direction — is how you end up either over-registered or exposed.

Where multi-channel sales tax gets genuinely tricky

Now add a second channel. This is where most sellers actually live.

Say you sell the same product on Amazon and through your own Shopify store. Amazon's facilitator status covers the Amazon orders. It does nothing for your Shopify orders. Direct-to-consumer sales from a site you control are your sale to collect and remit, full stop.

So the same SKU now lives under two different tax responsibilities:

• Marketplace orders: the platform collects and remits; you may still need to register and file an informational return.
• Direct (Shopify, BigCommerce, your own checkout): you collect, you remit, you file — in every state where your total activity crossed economic nexus.

And here's the part people miss on multi-channel sales tax: many states count your marketplace sales and your direct sales together when deciding whether you've crossed the nexus threshold. Your Amazon volume can be the thing that pushes your tiny Shopify storefront into a registration requirement in a state you've never visited.

A quick illustrative example

Consider a typical apparel seller doing $1.2M a year: $900K on Amazon, $300K direct on Shopify, shipping to all 50 states.

Amazon collects and remits on the $900K everywhere. Clean. But the seller crossed economic nexus in, say, 18 states on combined volume. In several of those, the $300K of Shopify sales is fully their responsibility to collect and file. Skip it, and the exposure isn't just the uncollected tax — it's penalties and interest stacking quietly for years.

Run that math at a blended 7% rate on uncollected Shopify tax across a handful of states and you're looking at a five-figure liability that nobody flagged, plus penalties. (Figures are illustrative, not a quote of any client's result.)

The Amazon side looked perfect the whole time. That's exactly why it gets ignored.

Marketplace facilitator laws explained, applied: staying clean across channels

The fix isn't complicated, but it does require someone tracking it on purpose:

• Map every channel to its tax treatment — facilitated vs. direct — instead of assuming the platforms cover you.
• Track combined economic nexus, because marketplace and direct sales often count together toward the threshold.
• File the boring zero returns in states that require them so an automated notice never turns into an audit.
• Re-check rules per state, since thresholds and marketplace-seller filing rules genuinely differ and change.

A generalist CPA who does a few eCommerce clients on the side will usually wave this off — "Amazon handles sales tax." A specialist won't.

Find an eCommerce CPA who actually tracks both sides

If you sell on a marketplace and direct, you don't have one sales tax problem. You have two, and they interact.

ECOM CPA works only with eCommerce sellers — Amazon, Shopify, Walmart Marketplace, the whole stack. That focus is the point: they've seen exactly how marketplace facilitator rules and direct-to-consumer nexus collide, and where the surprise notices come from.

Read ECOM CPA's verified reviews on Sam's List, then book an intro call before your next quarter closes. Sorting out a registration is cheap. Unwinding three years of unfiled returns is not.