FLEX. Fulfillment
Plain-English definitions of every Amazon and FBA term non-EU sellers encounter — from FNSKU and ASIN to Pan-EU FBA, EFN, IPI scores and removal orders.
This glossary covers the Amazon and FBA terms non-EU sellers encounter most often when shipping inventory to EU fulfilment centres or evaluating their Amazon selling strategy in Europe. Each term links to the full guide or service page that explains the mechanics in depth. For EU-specific prep and forwarding services, every entry connects to the relevant page on the FLEX. network.
Program & Model Terms
FBA (Fulfilment by Amazon) is a programme in which sellers send inventory to Amazon fulfilment centres (FCs) and Amazon handles storage, picking, packing, shipping, customer service and returns on their behalf. Under FBA, products become Prime-eligible automatically, which typically improves conversion rates and Buy Box competitiveness. In the EU, FBA inventory must meet specific prep requirements — labelling, poly-bagging, pallet dimensions — before Amazon accepts it. Amazon FBA prep services in Europe covers the full prep workflow FLEX. handles before inbound shipments depart for EU fulfilment centres.
FBM (Fulfilment by Merchant) is the model in which the seller, rather than Amazon, stores inventory and fulfils orders directly to customers. The seller is responsible for storage, picking, packing, shipping and customer service. FBM gives sellers full control over their fulfilment operation and avoids FBA storage and fulfilment fees, but products are not automatically Prime-eligible unless the seller qualifies for Seller Fulfilled Prime. FBM is a viable strategy for large, slow-moving, or hazardous products that are expensive to store at FBA rates, and as a backup for FBA stockouts.
Seller Fulfilled Prime (SFP) is a programme that allows sellers to display the Prime badge on FBM listings, provided they meet Amazon's strict SLA requirements: same-day or next-day dispatch, tracked shipping using approved carriers, and a cancellation rate below 0.5%. In the EU, SFP requires a fulfilment operation capable of consistently meeting those SLAs across the markets the seller is active in. Seller Fulfilled Prime fulfilment at FLEX. provides the infrastructure for sellers who want Prime eligibility without storing inventory at Amazon FCs.
Multi-Channel Fulfilment (MCF) is an Amazon service that allows sellers to use their FBA inventory to fulfil orders from non-Amazon sales channels — their own website, other marketplaces, or B2B customers. Amazon picks, packs and ships the order, but the packaging carries generic branding rather than Amazon branding. MCF is useful for sellers who want a single inventory pool across channels without operating their own warehouse. Omnichannel fulfilment service at FLEX. covers the 3PL alternative for sellers who need branded packaging or more flexible routing across channels.
Pan-EU FBA is a programme in which Amazon automatically redistributes a seller's FBA inventory across its EU fulfilment centre network — Germany, France, Spain, Italy, Poland and the Czech Republic — to position stock closer to where customer demand is highest. The benefit is lower fulfilment costs within each country. The obligation is VAT registration in each country where Amazon stores inventory, which can mean registrations in up to six EU member states. Sellers must assess whether the fulfilment fee savings outweigh the VAT compliance overhead before enrolling.
The European Fulfilment Network (EFN) allows a seller to store inventory in one EU country's FBA fulfilment centres and fulfil orders from Amazon customers across multiple EU marketplaces from that single pool. The fulfilment fee is higher than Pan-EU because Amazon is shipping cross-border to reach the customer, but the seller avoids VAT registration in multiple countries. EFN is the common starting point for sellers entering EU Amazon before they assess whether Pan-EU enrolment makes economic sense. Forwarding to Amazon FBA in Europe covers inbound logistics for both EFN and Pan-EU inventory pools.
The Buy Box is the default purchase button on an Amazon product listing. When multiple sellers offer the same ASIN, Amazon's algorithm selects one seller to hold the Buy Box at any given time — that seller captures the majority of sales on the listing. Key Buy Box factors include price (total including shipping), Prime eligibility, seller metrics (order defect rate, late dispatch rate, cancellation rate), and fulfilment method. FBA sellers generally have a structural advantage in Buy Box competition because Prime eligibility and Amazon's own fulfilment metrics are treated favourably.
Prime on an EU Amazon listing indicates that the product is eligible for fast, free delivery for Amazon Prime subscribers. Prime eligibility is automatic for FBA inventory and available to FBM sellers who qualify for Seller Fulfilled Prime. Prime-badged listings convert at significantly higher rates than non-Prime listings, and Prime is increasingly required to win the Buy Box on competitive ASINs. In the EU, Prime delivery promises vary by country — Germany and France have the most developed same-day and next-day networks.
Identifier & Labelling Terms
ASIN (Amazon Standard Identification Number) is a ten-character alphanumeric identifier that Amazon assigns to every product in its catalogue. Each unique product version — colour, size, bundle configuration — has its own ASIN. For books, the ASIN is the ISBN. Sellers must match their product to an existing ASIN if one exists, or create a new ASIN if the product is genuinely new to the Amazon catalogue. The ASIN is the unit of account for inventory, pricing, reviews and advertising — all seller activity on Amazon is organised around ASINs.
FNSKU (Fulfilment Network Stock Keeping Unit) is the barcode Amazon assigns to link a specific unit of inventory to a specific seller's account within FBA. It is required when a seller opts out of commingled inventory — where units from multiple sellers of the same ASIN are mixed — and instead keeps their stock separately attributed. FNSKU labelling is the default recommendation for most sellers because it prevents quality complaints from other sellers' defective stock being attributed to your account. Amazon FBA prep requirements in Europe covers FNSKU label specifications, placement rules and print quality requirements in full.
MSKU (Merchant SKU) is the seller's own internal identifier for a product as it appears in Seller Central. It is distinct from the ASIN (Amazon's identifier) and the FNSKU (the FBA label barcode). The MSKU is what the seller uses to manage their own catalogue, track inventory and create inbound shipment plans. A single ASIN can have multiple MSKUs if the seller manages variants or condition grades separately. Consistent MSKU naming conventions make inbound shipment planning and inventory reconciliation significantly easier at scale.
SKU (Stock Keeping Unit) is a generic retail term for a unique product identifier used by the seller or warehouse to track inventory. On Amazon, the SKU most commonly refers to the Merchant SKU — the seller-assigned code that identifies a product in Seller Central. In a 3PL or prep centre context, SKU is often used loosely to mean any unique product variant. When communicating with a prep centre, always clarify whether you mean MSKU, FNSKU or ASIN, as the three are distinct identifiers with different functions in the FBA workflow.
A Shipment ID is the reference number Amazon generates in Seller Central when a seller creates an inbound shipment plan. It identifies a specific batch of inventory being sent to one or more FBA fulfilment centres. The Shipment ID is used on all documentation — box content labels, pallet labels and the bill of lading — to match the physical shipment to the Seller Central plan at FC receiving. Forwarding to Amazon at FLEX. coordinates shipment ID management as part of the inbound logistics workflow.
ASN (Advanced Shipment Notification) is an electronic document sent to Amazon ahead of a physical inbound shipment, confirming the contents, quantities and expected arrival. For FBA inbound, the shipment plan created in Seller Central serves as the ASN. For Vendor Central (Amazon Vendor) shipments, the ASN must be submitted electronically through the Vendor portal and must match the physical delivery precisely — discrepancies between ASN and physical receipt result in chargebacks. Forwarding to Amazon at FLEX. handles ASN coordination for both FBA and Vendor inbound workflows.
A PRO label (also called a pallet label or LTL label) is the barcode Amazon requires on each side of every pallet in an FBA inbound shipment sent by less-than-truckload (LTL) or full truckload (FTL) freight. Four PRO labels are required per pallet — one on each face — applied to the outside of the stretch wrap so they are scannable without unwrapping. PRO labels are generated from the Seller Central inbound shipment plan. Amazon FBA prep requirements in Europe covers full pallet label specifications and placement rules.
Inventory & Fee Terms
A fulfilment centre (FC) is one of Amazon's warehouse facilities where FBA inventory is stored, picked, packed and dispatched to customers. Each FC is identified by a three-to-four letter code — such as FRA3 in Germany or CDG7 in France — which determines the prep, pallet and labelling specifications that inbound shipments must meet. Amazon assigns FCs automatically based on the seller's inbound shipment plan and product category. Amazon fulfilment center codes and locations lists every active EU FC code with its location and the prep centre routing FLEX. uses for each.
A removal order is an instruction sent from a seller's Seller Central account directing Amazon to remove specific inventory from an FBA fulfilment centre and either return it to a designated address or dispose of it. Sellers initiate removal orders to avoid long-term storage fees, recover unsellable inventory, or repatriate stock before it becomes stranded. Amazon removals and returns at FLEX. receives removal order returns, inspects and grades condition, and either relists, refurbishes or disposes of units according to the seller's instructions. For specialist removal processing see also Amazon removal orders in Europe.
Stranded inventory is FBA stock that is physically present in an Amazon fulfilment centre but is not linked to an active, buyable listing — meaning it is incurring storage fees without generating any sales. Common causes include a listing being deleted, suppressed or deactivated while inventory remains at the FC, or a product being restricted in a category without a valid exemption. Stranded inventory is visible in the Seller Central inventory health dashboard and must be resolved promptly — either by reactivating the listing or submitting a removal order — because Amazon charges storage fees on stranded units regardless of their listing status. Amazon removals and returns at FLEX. handles removal and recovery of stranded inventory.
Amazon's aged inventory surcharge (previously called the long-term storage fee) is an additional monthly fee applied to FBA inventory that has been stored in an Amazon fulfilment centre for more than 181 days (for standard-size) or 271 days (for oversize). The surcharge is assessed on the 15th of each month and is charged per cubic foot on top of the standard monthly storage fee. The practical implication is that slow-moving FBA inventory becomes progressively more expensive to hold — sellers need to either sell down, discount aggressively, or remove aged inventory before it passes the surcharge threshold. Amazon FBA inbound fees in Europe covers the full fee structure including aged inventory surcharge rates.
IPI (Inventory Performance Index) is Amazon's composite score that measures how efficiently a seller manages their FBA inventory. It is calculated on a scale of 0 to 1,000 and reflects four factors: excess inventory ratio, sell-through rate, stranded inventory percentage, and in-stock rate for replenishable products. Sellers with IPI scores below Amazon's minimum threshold (typically around 400) face storage capacity limits at FBA, which restricts how much inventory they can send in. Maintaining a healthy IPI requires balancing inbound shipments against sell-through velocity to avoid both stockouts and excess aged inventory. Amazon FBA inbound fees in Europe explains how IPI affects restock limits and fee eligibility.
Restock limits are the maximum cubic feet of inventory that Amazon allows a seller to hold across all FBA fulfilment centres for a given product type (standard-size, oversize, apparel, footwear, etc.) at any one time. They replaced the previous ASIN-level restock limits system in 2021 and are directly tied to IPI score — sellers with low IPI scores receive lower capacity allocations. Restock limits affect how much inventory a seller can send in advance of peak season and constrain sellers who want to pre-position large quantities. Amazon FBA inbound fees in Europe covers restock limit mechanics and planning strategies.
The inbound placement fee (introduced as part of Amazon's Inbound Placement Programme in 2024) is a charge Amazon applies when a seller's inbound shipment is sent to a single FC rather than distributed across Amazon's fulfilment network. Amazon prefers sellers to split shipments across multiple FCs to reduce its own internal transfer costs; if a seller sends everything to one location, Amazon charges a placement fee to cover the redistribution it then performs internally. Sellers can avoid or reduce the fee by opting into Amazon's multi-FC split at the shipment plan stage, accepting the logistics complexity of shipping to multiple locations. Amazon FBA inbound fees in Europe covers placement fee rates and how to minimise them.
Long-term storage fee (LTSF) is an older term for what Amazon now calls the aged inventory surcharge — the additional monthly fee applied to FBA inventory stored beyond 181 days (standard-size) or 271 days (oversize). The fee is charged per cubic foot on the 15th of each month and increases significantly after 365 days of storage. LTSF/aged inventory surcharge management is a core part of FBA inventory hygiene — sellers typically combine sell-through promotions with removal orders to prevent inventory from crossing the surcharge thresholds. Amazon FBA inbound fees in Europe covers current aged inventory surcharge rates for EU FBA.
Reserved inventory is FBA stock that is currently committed to a customer order that is in process — being picked, packed or in transit to the customer — and therefore not available to fulfil additional orders. Reserved inventory appears as a separate quantity in the Seller Central inventory breakdown alongside available, inbound and unfulfillable quantities. It is a normal operational state; elevated reserved quantities during peak periods simply reflect high order volumes moving through the FC. Reserved inventory that remains elevated for extended periods without clearing can indicate FC processing backlogs worth monitoring through Seller Central performance alerts.
Related Services & Guides
Explore the FLEX. services and deep guides behind these terms:
- Amazon FBA prep services in Europe — FNSKU labelling, poly-bagging, pallet builds and kitting
- Amazon FBA prep requirements in Europe — full 2026 requirements guide for EU FBA inbound
- Amazon FBA inbound fees in Europe — placement fees, aged inventory surcharge, IPI and restock limits
- Forwarding to Amazon — shipment plan coordination and inbound logistics to EU FCs
- Amazon fulfilment center codes and locations — every active EU FC with routing information
- Seller Fulfilled Prime fulfilment — Prime-eligible FBM infrastructure from FLEX.
- Amazon removals and returns — removal order processing, inspection and relisting
- Amazon removal orders in Europe — specialist removal order handling at fbaremovals.eu
- Forwarding to Amazon FBA in Europe — EFN and Pan-EU inbound logistics at fbaforwarding.eu
- Omnichannel fulfilment service — MCF alternative for multi-channel inventory management
Located in the center of Europe, FLEX. Fulfillment provides Amazon FBA prep, forwarding, removal order processing and omnichannel fulfilment from warehouses in Germany, Poland and France.
Reach out to the FLEX. team today via our contact form for a no-obligation quote tailored to your product range and sales volume. A more profitable fulfillment strategy could be closer than you think.