FBA, FBM, or a 3PL: Who Stores the Product and Who Makes the Delivery Promise

Fulfillment is the promise on the product page, kept or broken. Fulfillment by Amazon, Fulfilled by Merchant, and a third-party logistics provider are three ways to keep it. They are not three tiers of seriousness. Brands get this wrong by picking FBA because it is famous, or by shipping from overseas because the unit cost looks lower, and then wondering why the offer is not featured.

AEG sets this up for brands, and for factories leaving a wholesale relationship with Amazon. The comparison below is structural. It is not a rate card. Amazon’s current fees belong on sell.amazon.com/pricing and in the 2026 fee letter. That letter says 2026 FBA fees rise by an average of about $0.08 per unit and that no new FBA fee types were added. Your size tier will not match the average. Use the Revenue Calculator.

What each option actually does

Fulfillment by Amazon. You send inventory to Amazon’s buildings. Amazon stores it, picks, packs, ships, and handles much of the customer contact and the return. You pay fulfillment fees that depend on size and weight, monthly storage, and, if units sit too long, aged-inventory surcharges. The delivery promise is Amazon’s, which is why FBA offers are often easier to feature. It is not a requirement. Amazon says Fulfilled by Merchant offers can be featured too. The inputs are price including shipping, delivery speed and certainty, in-stock status, and order experience. Source: Amazon’s Featured Offer article.

Fulfilled by Merchant. You, or a warehouse you pay, ship the order. You set the shipping price or you offer free shipping and bury the cost in the item price. The promise is yours. Miss it, and the metrics Amazon already uses for the featured offer move against you. FBM is the right tool for products FBA will not take, for made-to-order goods, for very slow sellers where FBA storage would dominate, and as a backup when FBA is out of stock.

A 3PL. A 3PL is a warehouse that is not Amazon. It can ship FBM orders, replenish FBA, ship Walmart or your store, and hold the inventory you do not want inside Amazon’s buildings. It does not, by itself, give you Amazon’s delivery promise. A 3PL plus FBM is still FBM. A 3PL that only replenishes FBA is a staging point, not a second channel.

Walmart adds a constraint. Walmart’s September 2026 onboarding guide requires either Walmart Fulfillment Services or a B2C warehouse in the United States. WFS itself requires inbound freight to ship from inside the US or to clear customs first. The details and the limits are in the cross-channel essay.

A former vendor’s version

On Vendor Central, Amazon ordered what it wanted and stored it. When you move to a seller account, nobody is going to place that purchase order for you. The overlap between leftover vendor stock and the first seller inbound is the dangerous window. It is described in the 1P-to-3P essay. The fulfillment choice has to be made before that window, not during it.

Practical pattern for a brand that is new to holding US inventory:

1. A 3PL, or a prep point, in the United States that can receive a container and book an FBA appointment.
2. FBA for the hero SKUs whose delivery promise has to match everyone else in the search result.
3. A small FBM backup on those heroes only if the 3PL can ship the same day you promise. A backup that ships in a week is not a backup. It is a late order.
4. FBM or 3PL-only for the odd sizes, the regulated items FBA restricts, and the wholesale orders that should never enter an FBA building.

Do not start with three buildings. Start with one path you can explain, then add the backup when the first path has missed a week.

What to compare, besides the fee

The fee matters, and it is not the only line.

• The promise you can keep. A cheaper FBM ship time that you miss will cost the featured offer. Price that in.
• Who holds the cash. FBA inventory is your cash, sitting in Amazon’s building, subject to storage and aged fees if you overshoot. A 3PL is also your cash. The difference is who can ship to which channel.
• Returns. FBA returns are operationally easy and can put a damaged unit back into your sellable inventory if you are not watching. Inspect the returns report. A 3PL return is slower and usually clearer.
• Multi-channel. If Walmart and the store matter this year, a 3PL that can see all three, replenishing FBA from the same pool, is simpler than three separate stocks. It is also a forecasting problem. The forecasting essay is that problem.
• Compliance. Hazmat, meltable goods, expiration dates, and adult products have FBA rules that a blog post should not paraphrase from memory. Read the current FBA help page for the category before you book the container.

A decision rule

Use FBA when the product is a standard, in-stock, comparable item and the delivery promise is part of why a shopper will choose it. Use a 3PL plus a short FBA cover when you also sell off Amazon and you do not want every unit trapped in one program. Use FBM alone when you can ship as fast as you promise and the product does not fit FBA.

If you cannot say, in one sentence, who ships a US order tomorrow morning, you do not have a fulfillment model yet. You have a freight forwarder.

A note on shipping from the home country

Seller-fulfilled orders that ship from outside the United States can be legal and still be a bad offer. Transit time shows up in the delivery promise Amazon compares. Duties, which a shopper may now owe because de minimis treatment is suspended, show up as a surprise. Neither helps a brand that is trying to look established. If the volume does not yet justify US inventory, say that the offer is a test and price it as one. Do not present an overseas parcel as the same promise an FBA unit makes.

Book a strategy call

If the US inventory plan is still “we will see,” send a brief or Book a strategy call.