1. FBM vs FBA: when to choose which
The FBM versus FBA decision usually gets reduced to “FBA for speed, FBM for control”. That is the headline but it misses the cost maths.
FBA (Fulfilled by Amazon) means Amazon stores your inventory, picks, packs, and ships every order. You pay storage fees per cubic foot per month, fulfilment fees per unit shipped, and additional fees for long-term storage, removal orders, and oversize items. The fulfilment fee for a small standard item under 500g is typically around £2.80 in 2026. The storage fee is around £21 per cubic metre per month off-peak, rising to £37 in Q4.
FBM means you store the inventory yourself (or pay a 3PL to do it), you pick and pack the order, and you select the carrier. Your costs are your warehouse rent or 3PL fees, your labour cost per pick, your packaging, and your carrier rates. For most UK sellers shipping under 2kg domestic, Royal Mail Tracked 48 lands the order for £2.50 to £3.50 depending on volume.
The cost cross-over depends on three variables. Storage velocity (how long stock sits before selling), unit weight (FBA fees scale steeply above 1kg), and SKU count (each SKU adds a removal cost if it does not sell). High-velocity small-and-light SKUs almost always work out cheaper on FBA. Low-velocity, oversize, or high-value SKUs almost always work out cheaper on FBM. The middle is where seller judgement matters.
A few situations where FBM wins regardless of the maths:
- Multi-channel inventory. Selling the same SKU on Amazon, eBay, your own Shopify store, and TikTok Shop. Single-pool inventory through FBM avoids the duplicate stock you need under FBA to cover the Amazon channel.
- Restricted products. Some product categories Amazon does not accept into FBA, or accepts at heavy fee premiums.
- Bundles and configured products. Configurable items (build-to-order, monogrammed, made-to-measure) cannot be pre-stocked at an FBA warehouse.
- Margin-thin commodity SKUs. A £4.99 SKU at 30% margin cannot absorb a £2.80 FBA fulfilment fee.
- Seller Fulfilled Prime. You qualify for the Prime badge while keeping FBM economics, if you can hit the metrics.
The Velocity Sellers case study on this site illustrates a real outcome: an FBM-heavy seller eliminated £12,000 a month in penalty fees by reorganising their dispatch around the right metrics. The seller did not move to FBA. They fixed the FBM workflow.
2. The four Amazon FBM metrics that matter
Amazon measures FBM seller performance on roughly twelve metrics in Seller Central. Four of them determine whether you keep selling.
| Metric | Threshold | What it measures | Below threshold triggers |
|---|---|---|---|
| Late Shipment Rate (LSR) | Below 4% | Orders confirmed shipped after the dispatch deadline | Account review, suspension if sustained |
| Pre-Fulfilment Cancel Rate | Below 2.5% | Orders cancelled by the seller before shipment | Account review, listing suppressions |
| Valid Tracking Rate (VTR) | Above 95% | Orders with a valid tracking number that scans | Loss of Prime, account review |
| On-Time Delivery Rate (OTDR) | Above 97% | Orders delivered on or before the estimated delivery date | Account review, loss of Prime |
A few operator notes on each.
Late Shipment Rate (LSR). Calculated over both the trailing 10-day and 30-day windows. The 4% threshold is per window. A single bad batch can spike the 10-day rate even if the 30-day rate looks healthy. The clock starts when the order is placed and ends when you confirm dispatch in Seller Central. Confirming dispatch a day late counts as a late shipment even if the parcel arrives on time.
Pre-Fulfilment Cancel Rate. Almost entirely driven by stock-outs. The fix is inventory hygiene, not dispatch. If you list a SKU on Amazon, the SKU has to be in stock or marked unavailable before an order comes in.
Valid Tracking Rate (VTR).A tracking number is valid if it scans through a carrier's tracking system within 48 hours of the dispatch confirmation. Royal Mail, DPD, Evri, Amazon Shipping, and Parcelforce all push scan events back to Amazon through approved feeds. Untracked services (Royal Mail Second Class without tracking) cannot meet VTR. If you use them on Amazon orders, VTR drops below 95%.
On-Time Delivery Rate (OTDR).Measures whether the parcel was scanned as delivered on or before the estimated delivery date Amazon shows the buyer. This is the metric most exposed to carrier variability. Amazon's estimated delivery date factors in your handling time and the carrier's typical transit time. A carrier delay you cannot control still affects your OTDR.
The thresholds above are public Amazon policy as of May 2026. Amazon publishes them in Seller Central under Performance > Customer Service Performance. Each metric has its own dashboard.
3. Buy Shipping through Amazon: what it protects
Amazon Buy Shipping is a label-purchasing service inside Seller Central. You select the order, choose a carrier and service from Amazon's pre-approved list, and Amazon generates the label. The label is paid for through your seller account.
The compelling part of Buy Shipping is what it protects.
If you ship every order through Buy Shipping by the dispatch deadline, Amazon takes responsibility for:
LSR protection
Confirmed shipped through Buy Shipping by the deadline = not a late shipment, regardless of carrier delay.
VTR protection
Tracking numbers from Buy Shipping are valid by definition. The tracking event feed is wired into Seller Central automatically.
OTDR protection
Buy Shipping bookings carry an Amazon estimated delivery date that aligns with the carrier's published transit time. OTDR is calculated against that date, so a carrier delay does not automatically penalise you.
What Buy Shipping does not do:
- Give you the best rate. Buy Shipping rates are negotiated by Amazon and are reasonable but not always the cheapest option on the market.
- Cover non-Amazon orders. Your eBay, Etsy, TikTok Shop, and Shopify orders are not in Buy Shipping.
- Handle multi-piece or palletised shipments cleanly. Buy Shipping is built for parcels.
- Cover specialised services. Premium delivery, Saturday delivery, or specific carrier services that are not in Amazon's pre-approved list.
The headline carriers in UK Buy Shipping are Royal Mail (Tracked 24, Tracked 48, Signed), Amazon Shipping, DPD, Evri, and DHL Parcel UK. The exact list and rates vary by seller, account size, and time. For most UK Amazon sellers, Buy Shipping covers around 80% of orders effectively. The remaining 20% (multi-piece, premium services, non-UK destinations) need a different carrier route.
A third-party multi-carrier shipping platform sits alongside Buy Shipping rather than replacing it. The pattern most professional sellers use: Buy Shipping for the standard Amazon-domestic orders, a multi-carrier platform for the edge cases and the other marketplaces.
4. Carrier selection for FBM
There are five carrier choices that cover almost all UK domestic FBM volume. Each one matches a different combination of weight, speed, and Amazon listing promise.
| Carrier service | Price band (1kg) | Delivery | Best for | Metric notes |
|---|---|---|---|---|
| Royal Mail Tracked 48 | £2.50–£3.50 | 2-3 working days | Standard FBM under 2kg, low-value | VTR-compliant, LSR-compliant |
| Royal Mail Tracked 24 | £3.50–£4.50 | 1-2 working days | Expedited FBM, fast-shipping items | VTR, LSR, SFP-eligible |
| Royal Mail Signed | £4.50–£6.00 | 1-2 working days | High-value, compensation tier | VTR-compliant |
| DPD Next Day | £5.50–£7.50 | Next working day | Expedited, parcels above 2kg, SFP | VTR, LSR, SFP-eligible |
| Evri Standard | £2.30–£3.20 | 2-4 working days | Sub-£10 items, weight-sensitive | VTR-compliant, OTDR risk at peak |
| Amazon Shipping | £2.50–£4.50 | Next day or 2-day | Amazon orders qualifying for Amazon Shipping | All metrics protected via Buy Shipping |
| Parcelforce Express24 | £6.50–£9.00 | Next working day | Heavy parcels (over 5kg), business addresses | VTR-compliant |
Price bands are illustrative and dependent on volume, account, and surcharges. Highlands & Islands, Channel Islands, and Northern Ireland all attract surcharges. Verify your own rate card.
The decision logic. The right carrier choice for an FBM order is a function of three variables: the listing's promised dispatch speed, the parcel weight and dimensions, and the destination postcode.
- A 200g sub-£10 item listed as “Standard delivery 3-5 working days” goes Evri Standard or Royal Mail Tracked 48.
- A 500g item listed as “Expedited 1-2 working days” goes Royal Mail Tracked 24.
- A 3kg item to a residential address listed as “Next-day” goes DPD Next Day.
- A 200g item to a Highlands & Islands postcode listed as “Standard” goes Royal Mail Tracked 48 (the only carrier without an out-of-area surcharge at that weight).
The mistake most FBM sellers make is to default to a single carrier across all SKUs and listings. Royal Mail Tracked 48 works for the £5 cable but is overkill for the £30 sneaker listed as next-day. Rate shopping per order against your active carriers is the lever that controls dispatch cost on FBM at scale.
5. Label format and tracking number compliance
Amazon enforces label format requirements through its Buy Shipping integration and through the tracking number formats it accepts in Seller Central. Get this wrong and you trigger Valid Tracking Rate failures, which lead to Prime suspensions and account reviews.
The technical requirements.
Tracking number format. Each approved carrier has a published tracking number format. Royal Mail Tracked 24/48 use a 13-character alphanumeric format (XX123456789GB). DPD uses a 14-digit numeric format. Amazon Shipping uses a TBA prefix followed by 13 digits. If you upload a tracking number that does not match the expected carrier format, Seller Central rejects it and the order shows as untracked. Untracked orders drop your VTR.
Carrier selection in Seller Central.When you mark an order as shipped outside Buy Shipping, you select a carrier from the drop-down. That carrier has to match the tracking number format. Marking an order as “Royal Mail” while uploading a DPD tracking number is one of the most common causes of VTR failures.
Scan events. Valid tracking requires the carrier to push scan events back to Amazon. Major UK carriers do this through approved EDI feeds. If you use a smaller carrier that does not have an Amazon integration, the tracking number may be technically valid but the scan events will not flow back, and VTR drops accordingly. Royal Mail, DPD, Evri, Parcelforce, DHL Parcel UK, and Amazon Shipping all integrate. Smaller regional couriers often do not.
Label format requirements. Some Amazon programmes (notably Seller Fulfilled Prime) require specific label formats with the Prime branding. Standard FBM does not require Prime-branded labels but the address block has to be legible, the tracking barcode has to scan, and the carrier-specific information block has to be present and correct. Carrier label PDFs printed at the wrong size (A4 instead of 4x6, or 4x6 instead of 4x4) cause carrier rejections at the depot.
The operator pattern that works. Use Buy Shipping for everything you can. For the orders Buy Shipping cannot handle, generate the label through a multi-carrier platform that abstracts the per-carrier format differences. Print the label in the format the carrier requires. Write the tracking number back into Seller Central through the Amazon Selling Partner API rather than the manual upload screen, which is the most common source of typos.
6. Seller Fulfilled Prime: requirements and audit
Seller Fulfilled Prime (SFP) is Amazon's programme that lets FBM sellers display the Prime badge on their listings without using FBA. The seller fulfils the order themselves but commits to Prime-level delivery speed and service. It is the most demanding FBM programme Amazon runs.
The headline requirements as published by Amazon in 2026:
- Delivery speed. Standard Prime offers Two-Day and Next Day delivery options on listings. SFP sellers must offer at least one Prime-eligible speed.
- Dispatch metrics. On-Time Delivery Rate above 99%, Valid Tracking Rate above 99%, and Cancel Rate below 0.5%.
- Weekend dispatch. Saturday dispatch (and Sunday in some markets) is required, not optional.
- Approved carrier list. SFP shipments must use Amazon-approved carriers and services. In the UK that is typically Royal Mail Tracked 24, Royal Mail Special Delivery, DPD Next Day, and Amazon Shipping.
- Buy Shipping use. SFP shipments must be booked through Buy Shipping (or an equivalent Amazon-approved automated label source).
- Trial period. New SFP applicants serve a trial period (typically 30 days at the time of writing) during which Amazon audits performance against the metrics. Falling below threshold during the trial means re-application.
The economics of SFP. The Prime badge typically increases conversion on a listing by a material margin, varying widely by category. Sellers stay in SFP because the conversion uplift outweighs the cost of the tighter operational requirements. Sellers leave SFP because they cannot sustain the metrics at peak (Black Friday, Christmas) and would rather drop the badge than risk a permanent suspension.
The audit risk. Amazon runs continuous performance audits of SFP sellers. Falling below any of the headline metrics for a sustained period triggers a review that can lead to removal from the programme. The recovery path from an SFP suspension is long and not always successful. The operational discipline required to maintain SFP is the same discipline that protects standard FBM seller status: real-time order routing, automated carrier selection by service type, tracking write-back via the API rather than manual upload, and continuous metric monitoring.
For a high-volume seller, SFP is the highest-performing form of FBM. For a seller without the workflow to support 99% OTDR consistently, SFP is a fast route to a suspension. The honest answer to “should we apply for SFP” is usually: get your standard FBM metrics to consistent 98% first, then apply.
7. Managing FBM at scale
The manual FBM workflow breaks at predictable volumes. Knowing where the breakpoints sit helps you plan the next tool change before the metrics start sliding.
| Daily order volume | Typical workflow | Where it breaks |
|---|---|---|
| Up to 50/day | One operator logs into Seller Central, prints Buy Shipping labels manually, packs, ships. | Holiday cover. One sick day and the dispatch deadline slips. |
| 50 to 200/day | Two operators sharing Seller Central, batch label printing through Buy Shipping, basic SKU-to-bin mapping. | Cross-channel orders. Amazon orders get the Buy Shipping workflow but eBay and Etsy go through different label processes. |
| 200 to 1,000/day | A WMS or order management system (Linnworks, Selro, Veeqo, Mintsoft) handling cross-marketplace order import and label generation. | Carrier selection logic. A WMS without rate shopping defaults to one carrier per channel. |
| 1,000+/day | Order management system, multi-carrier platform for label generation, dedicated dispatch team, possibly 3PL outsourcing. | Workflow ownership. The seller stops being the operator and starts being the workflow designer. |
The transitions are not just about volume. They are about how many marketplaces you are on, how many carriers you are using, and how variable your SKU mix is. A seller doing 800 orders a day on Amazon alone with three SKUs is a simpler operation than a seller doing 300 orders a day across Amazon, eBay, Etsy, TikTok Shop, and their own Shopify store with 200 SKUs.
The dispatch deadline is the operational anchor. Most Amazon orders carry a same-day-dispatch promise if placed before a 14:00 or 16:00 cut-off. eBay and Etsy have their own cut-offs. Every order in the queue has a deadline, and every deadline missed counts against the relevant marketplace's late shipment metric. As the marketplace count grows, the deadline mix gets harder to track manually. This is where the SLA-aware dispatch logic in a multi-carrier platform stops being a nice-to-have and starts being load-bearing.
8. Where a multi-carrier platform fits in
A multi-carrier shipping platform like Connexx is not a replacement for Amazon Buy Shipping. It complements Buy Shipping by covering everything Buy Shipping does not.
What a multi-carrier platform adds to an FBM workflow:
- Cross-marketplace dispatch in one queue.Amazon, eBay, Etsy, TikTok Shop, Temu, OnBuy, and your own Shopify store flow into a single dispatch queue with each order's SLA deadline visible. No tab switching.
- Rate shopping for non-Buy-Shipping orders. When Buy Shipping does not cover a service (premium delivery, multi-piece, international), the platform compares the active carriers and selects the cheapest compliant option. Royal Mail, DPD, Evri, Parcelforce, DHL Parcel UK, Amazon Shipping, and others.
- SLA-aware routing.The platform knows each marketplace's dispatch deadline (Amazon's 16:00 cut-off, eBay's varies by listing) and surfaces the orders against their deadlines.
- Label format abstraction. One label format on the print queue. The platform handles the per-carrier label format conversion behind the scenes.
- Tracking write-back. Tracking numbers flow back to Amazon, eBay, and the other marketplaces via API. The Valid Tracking Rate and equivalent metrics on other platforms stay clean without manual upload.
- Penalty fee traceability. When a penalty fee invoice lands, the platform can trace the cause back to the specific shipment, carrier, and SLA breach in minutes rather than hours.
The Velocity Sellers case study illustrates the outcome. A multi-marketplace seller hitting £12,000 a month in penalty fees moved their dispatch onto a single multi-carrier workflow. Penalty fees dropped to zero. Fulfilment time dropped from 72 hours to 24 hours. Seller ratings went from 94% to 99.2%. The seller did not move to FBA. They fixed the FBM workflow.
For more on how this works in practice, see our marketplace seller solution page.