How to choose an Amazon FBA prep center
Five questions every seller should ask before committing volume. Plus the questions that look smart but aren't, and what a good answer actually looks like for each.
Most sellers pick a prep center the way they pick a 3PL: a Google search, three quotes, the cheapest per-unit rate. That math fails inside the first quarter. Storage rates that weren't disclosed up front add up, Q4 turnaround stretches past what the contract promised, and the portal turns into a spreadsheet exercise that costs your team more time than the prep itself.
The five questions below are the ones our editor team asks every operator before considering them for our directory. They surface the pricing structure, speed, integration, category fit, and storage economics in the first 30 minutes of a call, and they tell you whether the operator is built for your business or someone smaller.
Use this as a buyer's checklist for any prep center, including ones outside our directory. The answers compose into a comparison matrix you can hold up against three operators side by side.
What's your per-unit rate at my projected monthly volume?
Sticker rates rarely apply. The number that matters is the rate at your volume tier, plus the next breakpoint so you can see where the math improves as you grow. Most operators publish entry-level rates, but real margin lives at scale tiers, and the spread between tiers is where the long-term savings sit.
What a good answer looks like
- A specific per-unit rate tied to your monthly volume range (1,000 / 2,000 / 5,000 / 10,000+ units), not a one-size flat fee.
- Surcharges named explicitly: clothing, oversize, fragile, hazmat, bundles. Each with a real dollar number.
- Setup fees and monthly minimums disclosed up front, not surfaced after the contract.
- Membership tiers (free / paid) explained in terms of what changes between them: SLA, support level, dedicated account manager, priority handling.
Red flags
- "Contact us for pricing" with no anchor number on the public site. If they won't quote a range publicly, expect the negotiation to be tilted toward them.
- One flat rate with no volume tiering. Either they're small and lose money at scale, or they're inflating small-order rates to subsidize big sellers.
- Surcharges discovered after the first invoice. Bundles of 5 or fewer counting as 2 units of volume rate is a legitimate (and common) pricing rule. The problem isn't the rule, it's surprising you with it.
- Pricing pages last updated in 2023 or earlier. Means either the operator stopped maintaining the page or hasn't moved rates in two years (rare in this market).
Real benchmarks (from our verified directory)
Per-unit rates across the verified operators in our directory cluster around the following tiers at the time of writing:
- $1.10 to $1.30 per unit at 5,000+ units per month for wholesale prep with FNSKU labeling and inspection included. See McKenzie Services for a public membership-tier breakdown, or Heroic Prep for straight per-unit tiering.
- $1.70 to $2.50 per unit at 1,000 to 2,000 units per month, the most common starting tier.
- $2.25 to $4.25 per unit for DTC fulfillment or carton forwarding on smaller volume.
If the quote you're seeing is significantly outside these ranges, ask why. Either you're at an unusual volume or category, or the operator is mispriced relative to the market.
What's your typical inbound-to-shipment turnaround?
FBA delivery windows are tight, and Amazon penalizes late shipments through your IPI score and through inbound performance flags. Your real cycle time is operator turnaround plus carrier transit plus Amazon's receive window at the destination fulfillment center. Operators quote one part of that math, but you have to add the rest yourself to know if your inventory will land in time.
What a good answer looks like
- A specific SLA in hours or days, ideally with two numbers: normal and Q4 peak. "24 to 48 hours normal, 3 to 5 days Q4" is the right shape of answer.
- An explanation of how they batch and prioritize: first in first out by default, with a paid expedite option for time-critical shipments.
- Real-time tracking of work-in-progress shipments (status: received, queued, prepping, packed, shipped), not just an end-of-day email.
- Honest disclosure of past Q4 misses. Every operator at scale has had a Q4 incident. The good ones can tell you what happened and what they changed.
Red flags
- Vague answers: "usually a few days," "depends on volume," "we get it done fast." None of these are SLAs.
- No SLA in writing in the contract. A verbal "24 hours" isn't enforceable when peak hits.
- No Q4 protocol documented. Q4 doubles or triples volume; operators without a written plan tend to break in November.
- No way to see WIP status. If your only signal that a shipment shipped is the carrier tracking number, troubleshooting delays takes days of back-and-forth.
How to interpret
Build your real cycle math by adding three numbers: the operator's stated SLA, your carrier's typical transit (LTL or parcel) from the prep facility to the receiving FC, and Amazon's receive window (commonly 3 to 7 days during Q4, 1 to 3 days off-peak). If you're running thin inventory, double the operator SLA as your planning buffer.
Prep-center geography matters here too. East Coast centers ship into the East Coast FC cluster faster but cost more to feed from West Coast suppliers. We have a geography breakdown on the Amazon FC directory if you want to map your prep choice to your demand geography.
Do you integrate with Seller Central, or use a third-party portal?
Portal friction is a hidden tax on every shipment, and it compounds. Manual Seller Central uploads, spreadsheet handoffs, email-based work orders, all of these take your team's time on top of the prep center's fees. The operator's portal (or lack of one) is the daily user experience of your prep relationship.
What a good answer looks like
- Direct Seller Central API integration in the best case: shipments created, FNSKU labels printed, transport plans booked without you touching Seller Central.
- A clean operator portal with a real-time inventory dashboard if API integration isn't available. Should show received quantity, expected quantity variance, prep status per SKU, and shipped quantity per destination FC.
- Bulk-action workflows for multi-SKU shipments: bulk upload of FNSKUs, bulk approval of variance reports, bulk reprint of labels for damaged units.
- Webhook or API access if you run a tech-forward operation. Some operators expose a partner API that lets your OMS write shipments directly.
Red flags
- Email-and-spreadsheet workflow only. Means every shipment requires your operator's manual intake plus your manual reconciliation. Error rate climbs with volume.
- No way to demo the portal before signing. "We'll show you when you onboard" is a warning. Ask for a live walkthrough or a recorded demo of a real seller's dashboard.
- No bulk actions. If reprinting 200 FNSKUs requires 200 individual clicks, the portal was built for low-volume sellers and will break under your shipments.
- Proprietary portal with no export. Locks you in. If you ever want to leave, you'll have to manually rebuild your prep history from invoices.
How to interpret
Demo the portal before committing volume, every single time. Ask the operator to walk through three flows: (a) creating a new inbound shipment, (b) reconciling a variance between expected and received quantities, (c) reprinting labels for damaged units. If any of those takes more than five minutes in the demo, expect it to take longer in production.
Can you handle hazmat, FDA-restricted, or oversize items?
This is a gating question, not a follow-up. Most prep centers cannot handle hazmat (batteries, aerosols, flammables, lithium cells), and many cannot handle FDA-regulated products (supplements, cosmetics, food). Oversize and heavy items have separate handling rules and pricing. If you sell any restricted category today, or plan to expand into one, the answer here gates the entire relationship.
What a good answer looks like
- A specific yes or no per category, with a documented process for each yes. "Yes for lithium batteries up to 100 Wh" is better than "yes we can do batteries."
- DOT hazmat certification for any battery, aerosol, or flammable handling. Amazon's hazmat guidelines define what counts.
- FDA Food Facility Registration (FFR) number if they claim supplement or cosmetic prep. Verify it on the FDA registry, not just on their site.
- Insurance coverage that names restricted categories explicitly. General liability isn't enough for hazmat.
- Oversize handling: forklift availability, dock heights, pallet capacity. If they can't load a 53-foot trailer at their dock, oversize is out.
Red flags
- "We can do anything" without category-specific documentation. Means they haven't actually built the process.
- No FDA cert when claiming supplement prep. Selling supplements through an unregistered facility is a compliance liability that lands on you, not the operator.
- No DOT certification when claiming hazmat. Penalty for shipping hazmat without proper handling can run into five figures per shipment, and the seller is liable.
- Vague about insurance limits. Standard amounts (general liability of $1 million to $2 million per occurrence, cargo coverage of $100,000 per occurrence minimum) are the floor. Restricted categories often need more.
How to interpret
Plan for category expansion. Even if your current line is all standard-size, soft goods, will you sell electronics with batteries in 12 months? Will you add a supplement line? Switching prep centers costs you 30 to 60 days of onboarding overhead per move. Pick the operator whose category fit covers where you'll be in a year, not just today.
What are your storage rates after the first 30 days?
Storage is where "cheap prep" centers recover margin. Headline prep rates can be low precisely because storage rates are high or opaque, and inventory that sits at the prep facility (waiting for an inbound window, returns being processed, slow-moving SKUs) accrues storage charges quickly.
What a good answer looks like
- A published rate per cubic foot per month, the industry standard unit. Or a per-pallet per-month rate for pallet-storage operators.
- Clear tier structure: free in-transit storage for the first X days (typically 7 to 30), then standard storage rate, then long-term storage rate after a threshold (typically 90 to 180 days).
- A distinction between in-flight storage (units expected to ship within days) and dead storage (units sitting more than 30 days). Some operators charge differently for each.
- Transparent handling of seasonal storage. Q1 inventory glut after Q4 is when storage costs spike for sellers who over-ordered.
Red flags
- No published storage rate. Especially suspicious if the per-unit prep rate is unusually low.
- Per-unit storage charges. Rare and usually expensive compared to per-cubic-foot.
- Vague about long-term storage cutoffs. Get the day count and the rate change in writing.
- No comparison data to Amazon's own long-term storage fees. A good prep operator can tell you when it's cheaper to ship to Amazon vs. hold at their facility.
How to interpret
Calculate your annualized storage cost for typical inventory turnover. Multiply average inventory volume in cubic feet by the operator's per-cubic-foot rate, then multiply by 12. Compare to Amazon's long-term storage fee schedule for the same inventory window. For slow-moving SKUs that trigger Amazon's LTS fees, prep-center storage is often cheaper. For fast-moving SKUs you turn in 30 to 60 days, Amazon's storage is usually fine.
Things you don't need to ask.
A few questions get asked on every first call because they sound smart. They're not. Here's what to ask instead.
"Are you Amazon SPN certified?"
Amazon's Service Provider Network is a paid directory listing, not a quality audit. Operators pay to appear in SPN, and Amazon does not vet their work product. Some of the best US prep operators aren't in SPN. Some SPN-listed operators are mediocre. SPN tells you the operator paid for placement, nothing more.
"Will you sign an NDA?"
Yes. Every legitimate prep center will. NDAs are standard. The answer is 'yes,' which means the question is non-differentiating. You learned nothing about the operator.
"What's your insurance coverage?"
Standard amounts are $1 million to $2 million general liability per occurrence, $100,000 cargo coverage per occurrence. Almost every operator carries these. The right question isn't whether they have insurance, it's whether the coverage matches your inventory value.
"How long have you been in business?"
Domain age is a weak signal. New operators can be excellent. Old operators can be coasting on a brand they built in 2018 and haven't reinvested in. A 2-year-old operator with 20 named reviews from the last quarter is a better bet than a 10-year-old operator with no public review activity since 2023.
"Can you handle Q4 volume?"
Every operator says yes. The question is non-falsifiable until November. By the time you find out the real answer, your Q4 inventory is already committed.