Ecommerce operations glossary for Amazon, Walmart and Shopify

ACoS is ad spend divided by the sales those ads produced. If $300 of ads drives $1,000 of attributed sales, ACoS is 30%.

In practice, Amazon Ads reports ACoS for every Sponsored Products and Sponsored Brands campaign, and it is the number most ad teams manage to. Walmart Connect and most other ad platforms report ROAS instead, which is the same ratio upside down: a 30% ACoS is a ROAS of about 3.3. ACoS on its own does not tell you whether an ad sale made money. For that, compare it with your break-even ACoS, which depends on your margin per unit. A product with a 25% margin before ads loses money on every ad sale above a 25% ACoS, however good the ROAS looks in a report.

TACoS is ad spend divided by total sales, from ads and organic together. $3,000 of ads against $30,000 of total sales is a 10% TACoS.

In practice, TACoS shows whether advertising is building the business or just buying the same sales. If ad spend rises and total sales rise faster, TACoS falls and organic sales are growing. If TACoS climbs month after month while total sales stay flat, ads are replacing organic sales rather than adding to them. Operators watch it alongside ACoS: ACoS judges a campaign, TACoS judges the account. There is no platform benchmark. Vendor compilations put mature products around 5% to 15% and launches at 25% or more (Eightx, Jun 30, 2026, vendor estimate), but the right ceiling comes from your own contribution margin.

Break-even ACoS is the advertising cost of sales at which an ad-driven sale makes nothing after its costs. It equals contribution margin before ads divided by price.

In practice, it is the ceiling for every ad decision. A $30 product with $13.36 of contribution margin before ads has a break-even ACoS of about 44.5%. Every ad sale above that ACoS loses money on that sale, and every one below it adds margin. Teams use it to set target ACoS by product (usually well below break-even, so there is profit left) and to decide which products should not be advertised at all. Because fees differ, the same product has a different break-even ACoS on Amazon, Walmart and Shopify, and it moves whenever a fee changes, such as Amazon's 3.5% fuel and logistics surcharge from Apr 17, 2026.

Contribution margin is what a sale leaves after the costs that come with it: price minus landed cost, channel fees, shipping and ad spend. It is what pays for overheads and, after them, profit.

In practice, it is the number that tells you whether growth is helping. Revenue can rise while contribution margin per order falls, because fees, returns, shipping and ads grow faster than price. Operators track it by SKU and by channel, because a product can earn a healthy margin on Shopify and a thin one on Amazon after FBA fees. Many teams split it into three layers: after product and fees; after fulfillment and returns; after ads. A store with $2M in revenue and a falling contribution margin is often worse off than a store with $1M and a steady one.

A retainer is a fixed monthly fee for a written scope of work. It is how most agencies and operations teams price ongoing service.

In practice, the scope matters more than the number. Published 2026 Amazon agency retainers run from $1,500 to $3,000 a month for stores under $250,000 a year up to $15,000 to $25,000+ above $10 million, and many add 10% to 20% of ad spend on top (SupplyKick, updated Sep 14, 2026, vendor estimate). When you compare retainers, list the tasks each one covers and its response times. Then check the term, the notice period and what happens to your data when it ends. A low retainer with a percentage of spend can cost more within a year than a higher fixed fee.

Fully loaded cost is the total cost of employing someone: salary plus benefits and payroll costs. We calculate it as salary divided by 0.70, because benefits are 30.0% of total compensation in US private industry (BLS, June 2026 data).

In practice, it is the number to compare with an outside fee. A $63,456 salary, the average for an ecommerce operations manager (ZipRecruiter, Sep 16, 2026), costs about $90,650 a year fully loaded. Recruiting, tools and the weeks the role sits empty come on top of that. Comparing a salary with a monthly fee understates the hire; comparing a fee with a fully loaded cost but ignoring the hours you spend managing an outside provider understates the provider. Count both sides the same way.

FBA is Amazon's fulfillment service: you send inventory to Amazon's fulfillment centers, and Amazon stores, picks, packs and ships each order and handles customer service and returns for those orders.

In practice, FBA fees rose an average of $0.08 a unit on Jan 15, 2026. Amazon said there would be no new FBA fee types in 2026 (Amazon, Oct 15, 2025). A 3.5% fuel and logistics surcharge on fulfillment fees followed from Apr 17, 2026. Amazon also stopped offering FBA prep and item labeling in the US from Jan 1, 2026, so units must arrive prepped and labeled by the seller or a prep center (Amazon developer changelog, Jul 28, 2025). FBA usually helps Prime eligibility and conversion, and it adds storage fees, aged inventory surcharges and receiving time to your planning.

An FNSKU is Amazon's fulfillment barcode. It ties a unit in a fulfillment center to the seller who sent it.

In practice, the rules changed for shipments sent on or after Mar 31, 2026, when Amazon ended commingling. Resellers, meaning sellers without the Brand Representative role in Brand Registry, must apply an FNSKU label to every unit, as must anyone whose products lack a manufacturer barcode or who has a GTIN exemption. Brand Representatives with valid GTINs no longer need stickers. Units that arrive without required barcodes are treated as defective and are not eligible for reimbursement. Labels must match the Seller Central format, with 0.25 inch of white space on the sides and 0.125 inch on the top and bottom (PPC Land, Mar 24, 2026).

Commingling was Amazon's practice of pooling identical units from different sellers under one manufacturer barcode, so Amazon could ship whichever unit was nearest to the buyer.

In practice, it ended for inbound shipments sent on or after Mar 31, 2026; inventory already in fulfillment centers before then was left as it was (PPC Land, Mar 24, 2026). For brands, the end of commingling removes a long-standing risk: a buyer receiving another seller's counterfeit or damaged unit under your listing. For resellers, it adds work, because every unit now needs an FNSKU label. Build labeling into your prep process and your receiving lead time, since unlabeled units are classed as defective.

The low-inventory-level fee is an Amazon FBA fee charged per unit shipped when a product's stock at Amazon runs too low compared with its sales.

In practice, it applies only when both your 30-day and 90-day historical days of supply are below 28 days (Amazon staff, Seller Forums). Amazon applies exemptions, and Seller Labs reports that new FBA products are exempt for their first 180 days of sales history and that the fee does not apply to oversize, apparel or hazmat products (vendor, updated Aug 3, 2026). The fee punishes running lean, while storage fees and aged surcharges punish holding too much. The working answer for steady sellers is to keep at least 28 days of supply at FBA, with reorder points that include receiving time.

The aged inventory surcharge is an extra monthly FBA charge on units that have been stored in a fulfillment center for 181 days or more.

In practice, the charge rises in steps as units age, and for 2026 Amazon added a top tier for stock held more than 15 months (Seller Labs, vendor, updated Aug 3, 2026). Check the current rates on your Seller Central fee page, because they change. The surcharge is why slow stock should be reviewed every month: by the time a SKU is a year old, holding it can cost more each month than removing it. Use the Inventory Age report to see which units are approaching each band, then decide to discount, remove or dispose before the next step.

Amazon's monthly storage fee is charged for the space your FBA inventory takes up, measured in cubic feet, at a rate that depends on size tier and month.

In practice, storage costs more from October to December than the rest of the year, so stock sent early for the holidays costs more to hold. Check the current rates on your Seller Central fee page before you plan inbound shipments. Cubic feet per unit equal length times width times height in inches divided by 1,728, so packaging size matters: a box an inch smaller on each side can cut storage noticeably across thousands of units. Storage, aged surcharges and the low-inventory-level fee together decide how much stock you should keep at Amazon.

The fuel and logistics surcharge is a 3.5% charge Amazon adds to fulfillment fees, not to the item's sale price.

In practice, it applies to US FBA fulfillment fees from Apr 17, 2026, about $0.17 a unit on average, and to Multi-Channel Fulfillment and Buy with Prime from May 2, 2026 (Digital Commerce 360, Apr 2026). Supply Chain Dive reported that it stays in effect until further notice and applies on top of the 2026 holiday peak fees. It is small per unit and large across a year: on 100,000 FBA units, about $17,000. Add it to every margin model and re-check break-even ACoS on low-margin products.

DD+7 means Amazon holds the funds from an order until 7 days after it is delivered, then releases them to your available balance. Amazon's own name for it is the Delivery Date Based Reserve.

In practice, it reached US and North American sellers on Mar 12, 2026, according to Amazon's notice as quoted by sellers and reported by EcomCrew (May 24, 2026). For a seller whose orders take four days to deliver, cash from each sale arrives about 11 days after the order, plus your disbursement schedule. That lengthens the cash conversion cycle and means less cash on hand for purchase orders. Plan a buffer into reorders, especially before peak season, and model it per channel rather than averaging it away.

An FBA reimbursement is a payment from Amazon for inventory it lost or damaged, or for certain customer returns and refunds that went wrong.

In practice, two rules shape it. Claims for units lost or damaged in fulfillment centers are due within 60 days of the item being reported lost or damaged, down from up to 18 months before Oct 23, 2024. And since Mar 31, 2025, Amazon reimburses at manufacturing cost rather than sale price, so keep "Manage your manufacturing cost" up to date (eComEngine, updated Mar 7, 2025, vendor). Recovery vendors estimate unclaimed reimbursements at 1% to 3% of FBA revenue, but the only reliable way to know is to check every month inside the window.

The returns processing fee is an Amazon FBA charge on certain customer returns, covering the cost of receiving and handling the returned unit.

In practice, which products and return rates trigger it is set out on Amazon's FBA fee pages in Seller Central, and the details change with Amazon's annual fee updates, so check your products in Fee Preview rather than relying on a summary. The useful habit is to watch return rate by ASIN every month. A listing that over-promises, a size chart that misleads or a product that arrives damaged will raise returns, and with them this fee, return shipping and lost resale value. Fixing the listing is usually cheaper than absorbing the fee.

Multi-Channel Fulfillment is Amazon's service for shipping orders from other sales channels, such as Shopify or your own site, out of your FBA inventory.

In practice, it lets one pool of stock at Amazon serve several channels, which simplifies inventory but ties those channels to Amazon's fees and rules. MCF fulfillment fees carry the 3.5% fuel and logistics surcharge from May 2, 2026 (Digital Commerce 360, Apr 2026). Before using MCF for Walmart orders, check Walmart's current policy on how its orders may be fulfilled and packaged. The operating risk with MCF is overselling: stock levels must sync quickly across every channel drawing on the same units. Check how MCF orders are packaged and labeled too, since some channels expect their own branding or none at all.

An inbound defect fee is a charge Amazon applies when an FBA shipment arrives with problems that make it harder to receive, such as missing or wrong box content information or labeling errors.

In practice, these fees are avoidable. They come from shipment data that does not match what is in the boxes, cartons that break Amazon's packaging rules, or units without the labels they need, which matters more since sellers became responsible for all prep and labeling from Jan 1, 2026. A short inbound checklist (correct box content, labels to spec, carton weights within limits, shipment plan matching the boxes) prevents most of them. Review inbound fees every month in your fee reports; a pattern usually points to one supplier or one prep step.

WFS is Walmart's fulfillment service for Marketplace sellers: you send inventory to Walmart's fulfillment centers and Walmart stores, picks, packs and ships each order.

In practice, the base fee for a standard item is $3.45 a unit at 1 lb or less, $4.95 at 2 lb and $5.45 at 3 lb. Items under 1 lb are weighed with 0.25 lb added for packaging and rounded up; items of 1 lb or more use the greater of unit weight and dimensional weight (length × width × height in inches ÷ 139). Surcharges add $0.50 for apparel, $0.50 for hazardous materials and $1.00 for items priced under $10. Storage is $0.75 per cubic foot a month, with extra charges in the fourth quarter and for stock older than a year (Walmart Marketplace Learn, updated May 27, 2026). WFS items can show faster delivery promises, which helps on Walmart's search.

The WFS long-term storage fee is Walmart's higher storage rate for inventory that has been in its fulfillment centers for more than a year.

In practice, from Jun 30, 2026 it is $2.25 per cubic foot a month for inventory stored 366 to 450 days and $7.50 for inventory stored more than 450 days. From October to December, inventory stored more than 30 days also carries an extra $1.50 per cubic foot a month (Walmart Marketplace Learn, updated May 27, 2026). At $7.50, a single month of storage can cost more than removing the units, which cost the disposal fee plus $0.40 per lb. Review WFS inventory age monthly and act before day 365.

Walmart's referral fee is its commission on each sale, a percentage of the total sales price that depends on the item's category.

In practice, Walmart sets the rate by the category and product type assigned at item setup: 15% for the Everything Else category, with each category at its own rate. The fee is calculated on the total sales price, which includes shipping, handling and gift wrap, so a high shipping charge raises it (Walmart Marketplace Learn, updated Mar 9, 2026). Walmart charges no setup or monthly fees (Walmart Marketplace). Check the category Walmart assigns, because a wrong product type can mean a wrong rate. On a $25 item with $5 shipping charged to the buyer, a 15% rate is charged on $30, so the fee is $4.50. Illustrative · sample figures.

Walmart's seller performance standards are the eight measures every Marketplace seller must meet to keep selling without restrictions.

In practice, the standards are: cancellation rate 2% or below, on-time delivery 90% or above, valid tracking 99% or above, seller response rate 95% or above, negative feedback 2% or below, return rate 6% or below (9% for resold items), item not received 2% or below and late shipment 5% or below. Missing them "may result in suppression, suspension or termination" (Walmart Marketplace Learn, updated Jul 28, 2026). Walmart emails sellers when performance slips, and those notices cannot be switched off. Check the dashboard daily on growing accounts. On-time delivery and valid tracking usually fail first on seller-fulfilled orders, which is one reason fast-growing accounts move top sellers to WFS.

An unpublished item is a Walmart listing that has been hidden from shoppers. It still exists in Seller Center but cannot be found or bought.

In practice, Seller Center shows each unpublished item with a reason code. Pricing is one of the most common: Walmart's Pricing Rule automatically unpublishes offers priced far above current or recent prices for the same item (Walmart Marketplace Learn, updated Dec 12, 2025), and once the price is corrected, the listing usually republishes within 48 hours (Riverbend Consulting, vendor, updated Aug 4, 2026). Other reasons include missing content, compliance issues and inventory problems. The habit that prevents lost sales is a daily check of the unpublished items report, so a hidden best seller is caught the same day.

Walmart's reasonable price rule, which Walmart calls the Pricing Rule, unpublishes offers priced far above prices currently or recently offered for the same item on Walmart.com or competing websites, looking at the listing price and shipping fee together (Walmart Marketplace Learn, updated Dec 12, 2025).

In practice, the offer is unpublished automatically with the reason code "Reasonable Price Not Satisfied", and Walmart says breaking its pricing rules may result in account suspension or termination. Shipping counts toward the total, so a fair item price with high shipping can still be flagged. The Unpublished Items dashboard shows Walmart's reference price, which is the number to work against (Riverbend Consulting, vendor, updated Aug 4, 2026). Repricers need floor and ceiling rules that respect it.

New-Seller Savings is Walmart's incentive program for new Marketplace sellers, worth up to $75K in incentives and benefits depending on the Walmart services used.

In practice, the program runs from Feb 2, 2026 to Jan 31, 2027. Sellers must go live after Feb 1, 2026. Referral fees are discounted 20% on your first $50K of GMV, 30% from $50K to $500K and 40% above that, and WFS fees are 10% off until you reach $2K in savings (Walmart Marketplace Learn, updated Sep 2, 2026). Conditions apply. Build the discount into your first-year margin plan, but price products to work at full fees too. Keep a record of your go-live date and GMV milestones so you can check the discounts on your settlement reports.

Brand Portal is Walmart's program for brand owners to register brands, submit intellectual property claims and keep brand content accurate on Walmart.com.

In practice, Walmart requires an active trademark registration with the USPTO for each brand (Walmart Marketplace). That means a registered mark, not just a filed application, so the trademark timeline matters: the USPTO's average time to a first action was 4.45 months in the first half of fiscal 2026 (USPTO, May 5, 2026), and registration takes longer. Brand owners can invite authorized users and assign update rights to authorized resellers. If you plan to sell on Walmart, file your trademark well before launch. Keep the registration certificate and the brand details you enter in Seller Center consistent, so the details Walmart checks match.

A Walmart Solution Provider is a company Walmart has approved to offer services or software to Marketplace sellers.

In practice, Walmart lists four types: full service, specialty, capital and agency, where an agency offers store management support (Walmart Marketplace Learn, updated Mar 6, 2026). Approved providers appear in Walmart's directory, and sellers connect them through Seller Center. Approval says a provider passed Walmart's process; it does not tell you about their pricing, terms or how they handle your access. Ask any provider, listed or not, for their scope, fees and access model in writing, and keep Admin on your Seller Center account yourself. Some sellers use several providers at once, for example an integration tool, a repricer and an agency, so write down who owns which task.

A GTIN (Global Trade Item Number) is the standard product identifier behind retail barcodes. A UPC is a 12-digit GTIN, the most common type in the US.

In practice, Walmart requires products to have GTINs or UPCs with GS1 Company Prefix numbers to list on its Marketplace (Walmart Marketplace Learn, updated Sep 2, 2026). Codes bought from resellers rather than issued through GS1 can fail verification. On Amazon, brand owners with valid GTINs no longer need FNSKU stickers for commingling purposes since Mar 31, 2026, which makes clean identifiers worth more. Buy them from GS1 in your company's name before you set up listings. Keep a simple register of every GTIN you own, the product it belongs to and every channel it is listed on, so codes are never reused.

Landed cost is the full cost of getting one unit into sellable stock: product cost plus freight, duty, customs fees, insurance and prep.

In practice, duty became the moving part in 2026. Since Jul 24, 2026, most covered imports face Section 301 tariffs of 10% or 12.5% depending on the country of origin, with exemptions (Morgan Lewis, Jul 27, 2026), and the $800 de minimis exemption no longer applies. A product that worked at last year's landed cost may not work now. Re-cost each SKU by country of origin, keep the calculation per unit and per shipment and update margins the day duty changes. Confirm classifications and rates with your customs broker.

De minimis was the US rule that let imports worth $800 or less per person per day enter without duty.

In practice, it was suspended for all countries from Aug 29, 2025. The One Big Beautiful Bill Act ends it by statute from Jul 1, 2027. On Aug 13, 2026, the Court of International Trade upheld the president's power to suspend it (Troutman Pepper Locke, Aug 18, 2026). For stores that shipped low-value parcels direct from overseas suppliers, every parcel now carries duty and customs processing. Treat de minimis as gone, build duty into landed cost and check whether bulk importing into a US warehouse now costs less than direct shipping.

A reorder point is the stock level at which you place the next purchase order, so new units arrive before the last ones sell.

In practice, the formula is average daily units × lead time in days + safety stock. For marketplace sellers, lead time includes supplier production, transit and the days FBA, WFS or a 3PL take to receive the stock. At 20 units a day, a 62-day lead time and 78 units of safety stock, the reorder point is 1,318 units. Illustrative · sample figures. Set reorder points per SKU and per location, and recalculate when sales speed, supplier lead times or receiving times change. Revisit reorder points before peak season, when both sales speed and receiving times usually rise at the same time.

Safety stock is the extra inventory you keep to cover days when sales run faster than average during the lead time.

In practice, the usual formula is Z × the standard deviation of daily units × the square root of lead time in days. Z sets the service level: 1.28 for 90%, 1.65 for 95%, 1.96 for 97.5% and 2.33 for 99%, from the standard normal table. Some calculators use 1.96 for 95%, which is the two-sided value and overstates safety stock. With a standard deviation of 6 units and a 62-day lead time, 95% service needs about 78 units. Illustrative · sample figures. More safety stock costs storage; less costs stockouts.

Days of supply is how many days your stock will last at the current sales rate: units on hand divided by average daily units sold.

In practice, it is the quickest way to see risk. Under your lead time means a stockout is coming; far above it means cash tied up and storage fees building. On Amazon, it also drives a fee: the low-inventory-level fee applies only when both your 30-day and 90-day historical days of supply are below 28 days. Track it per SKU and per location, because 90 days of supply in total can hide 10 days at FBA and 80 at your 3PL. Use a recent sales window that excludes days you were out of stock, or the number will look healthier than it is.

The cash conversion cycle is the number of days between paying for stock and getting paid for it: days of inventory plus days to collect minus days to pay suppliers.

In practice, a shorter cycle means less cash sitting in boxes and marketplace balances. Wayflyer, a lender, describes 60 to 120 days as typical for DTC brands and 30 to 90 days for Amazon sellers (Jul 15, 2024, vendor estimate). Amazon's payout 7 days after delivery since Mar 12, 2026 adds collection days, and supplier deposits paid before shipment push it out further. Each day cut frees about one day of cost of goods in cash. Measure it the same way every quarter so the trend is honest; the trend matters more than any benchmark.

Stockout cost is the margin you lose when a product is out of stock: the units you would have sold times your contribution margin per unit.

In practice, not every lost sale comes back. In a global study, 31% of shoppers facing an out-of-stock bought at another store, 26% switched brand and 9% bought nothing (FMI and GMA, Oct 14, 2002). On marketplaces, a stockout can also cost search rank that takes weeks to rebuild after the stock returns. At 20 units a day, a $9 margin and 66% of sales lost, each day out of stock costs about $119. Illustrative · sample figures. That is why stockouts on top sellers usually deserve attention before ad spend does: ads on an out-of-stock listing buy nothing.

Carrying cost is the yearly cost of holding inventory, expressed as a share of its value: storage, capital tied up, insurance, shrinkage and the risk that it never sells.

In practice, the textbook range is 20% to 30% of inventory value a year, attributed to ASCM, the supply chain association (Eightx, Jul 1, 2026, vendor). On marketplaces, storage fees and aged surcharges make the storage part explicit and seasonal. $40,000 of slow stock at 25% costs about $10,000 a year to keep. Illustrative · sample figures. Excess stock is not free just because it is already paid for. Review slow stock monthly and decide to discount, bundle, remove or dispose before the next storage band.