Every transaction on your platform has a legal seller, whether you named one or not. That entity is the merchant of record (MoR): the party the card networks, the tax authorities, and the cardholder treat as the one who actually made the sale. Get this wrong and you inherit liabilities you never priced into the take rate.
The earlier lessons in this module covered whether money flows through you (lesson 1) and how it splits at settlement (lesson 2). The MoR decision sits on top of both. It is not a payments-plumbing choice. It decides who answers for the sale when something goes wrong, and "something goes wrong" covers four distinct categories.
What the merchant of record actually owns
The MoR is the legal seller of the goods or service to the end customer. Four obligations attach to that role, and they travel together.
First, the customer relationship of record. The MoR's name appears on the cardholder's statement, and the MoR is the entity the buyer believes they bought from.
Second, sales tax. In the US the MoR is responsible for calculating, collecting, filing, and remitting sales tax on the transaction. In the EU and UK the equivalent is VAT.
Third, chargebacks and refunds. As the legal seller, the MoR carries the dispute. It receives the chargeback, builds the representment, and eats the loss if it cannot win. It also honors refunds.
Fourth, regulatory exposure. Consumer-protection rules, money-transmission questions, and anti-money-laundering obligations land on the entity presenting itself as the seller.
The MoR is whoever the cardholder, the tax authority, and the regulator can point at. You do not get to be the MoR for the take rate and not the MoR for the chargeback.
The two structures
There are two clean answers and a lot of expensive middle ground.
Seller as merchant of record
The platform stays an intermediary. Each seller is the legal merchant for their own sales, the seller's descriptor (or a clearly attributed version) shows on the statement, and the seller owns their own tax registration and dispute liability. This is the classic marketplace posture, and in payments terms it usually pairs with split settlement and seller-level onboarding (lessons 2 and 4).
The platform's job here is to make sellers boardable and keep itself out of the liability chain. The benefit is that exposure is distributed across thousands of sellers rather than concentrated on you.
Platform as merchant of record
The platform becomes the legal seller. Your name is on the statement, you collect and remit the tax, you own every chargeback, and you carry the regulatory weight. Amazon operates this way for many of its sellers: customers buy on Amazon, see Amazon on the statement, and receive Amazon-branded packaging.
This buys a clean, single-brand checkout and removes per-seller tax and compliance burden from the seller. It also concentrates all of that burden on you. That is the trade.
The card-network caveat
Be precise about terminology, because the networks are. The "merchant" in a card transaction is the party that represents itself as selling to the cardholder, identifies the storefront under its own name, and provides recourse in a dispute. The standalone "merchant of record" model, where a platform sells everyone's goods under its own name, is not expressly defined or sanctioned in card-brand rules and draws scrutiny around consumer protection and unlicensed money transmission.
The recognized, registered path for processing other parties' sales through one account is the payment facilitator (PayFac) model, which carries underwriting, monitoring, and registration obligations to the networks. Lesson 7 covers the PayFac-versus-marketplace-versus-orchestration choice in full. For now, hold this: if you intend to be the merchant for sales you do not originate, you need a structure the networks actually recognize, not a label you assigned yourself.
The tax dimension you cannot opt out of
US sales tax forces the issue whether you want it to or not. Since the Supreme Court decided South Dakota v. Wayfair on June 21, 2018, states can require sellers with no physical presence to collect tax once they cross an economic-nexus threshold. A common threshold is $100,000 in sales or 200 transactions in a state, though it varies; California, for example, sets its bar at $500,000.
On top of that, marketplace-facilitator laws now exist in nearly every sales-tax state. They make the marketplace, not the individual seller, responsible for collecting and remitting tax on sales made through the platform. So even if you intended sellers to own their own tax, the facilitator statutes may name you as the collector for marketplace sales. The platform also has to combine its own direct sales with marketplace seller sales when testing whether it has crossed a state's threshold.
The takeaway is blunt: in the US you are often pushed toward being the tax-collecting party for marketplace transactions by statute, regardless of which MoR structure you picked for everything else.
A worked example
A B2B parts marketplace launches with sellers as merchant of record. Sellers handle their own tax, and chargebacks flow back to each seller. Monthly volume hits $4 million across 600 sellers.
Three things surface. The marketplace-facilitator laws make the platform responsible for collecting and remitting sales tax on the marketplace sales, so the "sellers own tax" intent is partly overridden for in-state sales by statute. Separately, a fraud ring targets the platform, and because each seller is the MoR, dispute outcomes are uneven and several small sellers absorb losses they cannot represent against, then churn. Finally, buyers complain that 600 different statement descriptors look like fraud, raising the chargeback rate on legitimate sales.
The platform splits the difference. It becomes the tax-collecting facilitator (statute already required it), standardizes the statement descriptor for brand recognition, and provides centralized dispute tooling so sellers represent consistently, while keeping sellers as the MoR for chargeback liability. That mix is deliberate, not accidental, and it is documented per obligation.
The closing takeaway
Do not pick "platform MoR" or "seller MoR" as a single switch. Decide each of the four obligations on its own: statement identity, tax, disputes, and regulatory exposure. The law may already have decided the tax one for you. The other three are yours to assign, and the only wrong answer is leaving them unassigned until a chargeback or an audit assigns them for you.