Before the sale
The seller boxes and ships inventory to an Amazon fulfillment center, following Amazon's own prep and labeling rules for that shipment.
Amazon sellers and shoppers
How does Amazon shipping actually work?
An Amazon order ships one of two ways, and the choice gets made months before a shopper ever clicks buy. Fulfilled by Amazon (FBA) has the seller send inventory into Amazon's own warehouses in advance, and Amazon does the picking, packing and carrier hand-off from there. Fulfilled by Merchant (FBM) leaves all of that with the seller, who buys a shipping label through Amazon Buy Shipping and ships the box directly. Both paths can carry the Prime badge, just under different rules. Every quote below is sell.amazon.com's own wording, read 2026-08-31.
Amazon's own wordingRead 2026-08-31Live FBM label, 2026-08-31
Two programs, one storefront
Same listing page, two entirely different paths to the buyer's door.
Step one: the fulfillment choice happens before the sale
Every listing is assigned to one of two fulfillment programs when it is created, and that choice is what decides who touches the box after it sells. Under Fulfilled by Amazon, inventory is sent to Amazon ahead of any sale and Amazon fills every order from its own warehouse stock. Under Fulfilled by Merchant, the seller keeps the inventory in their own space and ships each order themselves once it sells, buying a label through Amazon's own shipping tool or an outside carrier account. A shopper cannot tell which program a listing uses just by browsing — the difference only shows up in who packs the box and how fast it can move.
Step two: what Amazon does inside FBA
Amazon's own FBA page, read 2026-08-31, describes the job in one line: “we'll pick, pack, and ship orders, as well as handle customer service and returns.” That covers the entire outbound leg — a seller who enrolls a product in FBA has no further shipping decision to make on any individual order once inventory is on Amazon's shelves.
At the sale
Amazon's own staff pick the item, pack it and hand it to a carrier, with no action required from the seller for that order.
After the sale
Amazon handles the customer service messages and any return, per the same page — not just the shipment itself.
Our separate page on what it costs to ship inventory into an FBA warehouse works through the inbound side of this — the leg that happens before any of the above, and the one a seller still prices and pays for directly.
Step three: what an FBM seller does instead
Amazon's own FBM program page, read 2026-08-31, puts the seller's job plainly: “Store, pack, and ship items that you prefer to fulfill yourself.” There is no Amazon warehouse standing between the sale and the shipment — the seller holds the inventory, and a sold order becomes a box the seller has to move.
Most FBM sellers buy that label through Amazon Buy Shipping rather than a separate carrier account. Amazon's own tools page, read 2026-08-31, describes it as a way to “Purchase shipping and print labels for UPS, Amazon Shipping, FedEx, USPS, and other major carriers—all in one place.” Nothing requires that route: a label bought anywhere else still moves the same box to the same buyer. Our separate page on Amazon shipping labels works through the one condition that route protects and an outside label does not.
Step four: Prime's badge is not one rule for both paths
Prime eligibility is not a single switch every seller flips the same way. Amazon's own FBA-versus-FBM comparison, read 2026-08-31, tells sellers to “Enroll products in FBA to get the Prime badge” — for that path, the badge follows the inventory automatically. An FBM seller can still earn Prime eligibility through Seller Fulfilled Prime, but only by first meeting Amazon's own delivery-performance bar and completing a trial period; it is not available the moment a listing goes live the way FBA's is.
Our separate page on what Amazon Prime actually promises on delivery works through what that badge means for a shopper at checkout, item by item and speed by speed.
A real FBM label, priced live on 2026-08-31
We told the SMKlog calculator a Logitech wireless mouse had sold as a Fulfilled by Merchant order and gave it Berkeley Heights, NJ to Chicago, IL. It estimated a 9 × 6 × 3 in box at 1 lb packed and returned five live services, unedited.
| Carrier | Service | Price | Quoted transit |
|---|---|---|---|
| USPS | Ground Advantage | $9.91 | 3-4 business days |
| UPS | Ground | $10.31 | 2-3 business days |
| USPS | Priority Mail | $14.49 | 3-4 business days |
| UPS | 3 Day Select | $15.13 | 2-3 business days |
| UPS | 2nd Day Air | $15.38 | 2-3 business days |
USPS Ground Advantage won this lane on a light, small box, which is typical under about two pounds. This is a standalone carrier label, priced the same way SMKlog prices any other US domestic parcel — not a Buy Shipping rate, which only appears inside a seller's own Seller Central account.
Where these rules come from
- Amazon, Fulfillment by Amazon (FBA) — what Amazon does after inventory arrives, and FBA's Prime eligibility. Read 2026-08-31.
- Amazon, Fulfilled by Merchant (FBM) — the seller's own storing, packing and shipping job, and the pointer to Amazon Buy Shipping. Read 2026-08-31.
- Amazon, Amazon Buy Shipping — the carriers a seller can buy labels for through the tool. Read 2026-08-31.
- Amazon, FBA vs FBM: Which is right for you? — the Prime badge rule for FBA and the Seller Fulfilled Prime alternative for FBM. Read 2026-08-31.
- Prices: our own capture against production for the mouse parcel above, Berkeley Heights, NJ 07922 to Chicago, IL 60601, run 2026-08-31.
Amazon revises its seller-program pages without notice. Treat the wording above as what was published on the date shown, and check Seller Central directly before relying on a detail here.
Amazon shipping questions
Does Amazon ship every order itself?
No. An order ships one of two ways depending on which program the seller chose for that listing. Fulfilled by Amazon (FBA) sends inventory into Amazon's own network ahead of time and Amazon packs and ships every order from there; Fulfilled by Merchant (FBM) leaves the box with the seller, who buys and prints the label themselves. Per sell.amazon.com's own comparison of the two, read 2026-08-31, FBA outsources packing, shipping, customer service and returns, while FBM keeps a seller shipping products directly to customers.
What does Fulfilled by Amazon actually do for a seller?
Everything after the inventory reaches an Amazon warehouse. Amazon's own FBA page, read 2026-08-31, states it directly: we'll pick, pack, and ship orders, as well as handle customer service and returns. A seller's job stops at getting inventory into the fulfillment network; Amazon's own staff and carrier accounts handle every order that sells out of it.
What does a Fulfilled by Merchant seller have to do themselves?
The whole outbound leg. Amazon's own FBM program page, read 2026-08-31, describes the job directly: sellers store, pack, and ship items that you prefer to fulfill yourself. Most FBM sellers buy that label through Amazon Buy Shipping, which Amazon's own tools page, read 2026-08-31, describes as a way to purchase shipping and print labels for UPS, Amazon Shipping, FedEx, USPS, and other major carriers, all in one place. Our separate page on Amazon shipping labels works through what buying it there protects that an outside label does not.
Does every Amazon listing get the Prime badge?
No, and the two fulfillment paths earn it differently. FBA earns the badge automatically: Amazon's own FBA-versus-FBM comparison, read 2026-08-31, tells sellers to enroll products in FBA to get the Prime badge. An FBM seller can still earn it through Seller Fulfilled Prime, but only after meeting Amazon's own delivery-performance requirements and a trial period, not the moment a listing goes up. Our separate page on what Amazon Prime actually promises on delivery works through what that badge means for a shopper at checkout.
What does an FBM seller's own label actually cost?
It depends entirely on the box. On a one-pound wireless mouse we quoted live from Berkeley Heights, NJ to Chicago, IL on 2026-08-31, five services ran from $9.91 to $15.38, cheapest on USPS Ground Advantage. A heavier or bulkier item moves those numbers in either direction, the same as any other domestic parcel.