How to Switch 3PLs Without Missing Orders

Most sellers stay too long with a fulfillment provider they've outgrown, because the migration feels riskier than the problem. It doesn't have to be — if you overlap the two warehouses instead of hard-cutting between them.

The fear is specific and reasonable: inventory stranded in the wrong warehouse, orders going unfulfilled during the handoff, tracking numbers not flowing back to customers, and a week of angry emails. Every one of those is avoidable with sequencing.

The core principle: never let there be a moment when neither warehouse can ship. That means a deliberate overlap period where both are live, not a clean break on a Friday night.

Before you move anything

Read your current contract

Check three things specifically: notice period, termination fees, and — the one that bites people — outbound removal fees. Some 3PLs charge per pallet or per unit to release your own inventory back to you. Know that number before you commit to a date, because it changes the real cost of leaving.

Also confirm who pays freight to move inventory out, and how much notice they need to prepare a pickup.

Get a real inventory count

Pull a current on-hand report from your existing provider and reconcile it against your own records. Discrepancies are common, and you want to find them before stock is in transit and impossible to audit. If the numbers don't match, resolve it while the inventory is still sitting on their shelf.

Identify your slow movers

A migration is a natural moment to stop paying storage on inventory that isn't selling. Sort your SKUs by turn rate. Anything that hasn't moved in six months, decide now: liquidate it, take it in-house, or accept that you'll keep paying to store it somewhere. Don't pay freight to move dead stock to a new warehouse.

The overlap migration, step by step

Step 1: Onboard the new provider while the old one still ships

Set up the account, connect the store integration, and get their system configured — all while your current 3PL continues fulfilling normally. Nothing is at risk yet. This is also when you discover whether the new provider is actually responsive, at a stage where finding out costs you nothing.

Step 2: Send new inventory to the new warehouse

Don't start by moving existing stock. Start by routing your next inbound purchase order — or a portion of it — to the new provider. This tests their receiving process with real product and no time pressure, and starts building stock there naturally.

Step 3: Split fulfillment by SKU

Once the new warehouse holds real inventory, move a small set of SKUs over to fulfill from there — ideally low-volume, non-critical ones. Both warehouses are now live. Watch how the new provider actually performs: turnaround time, packing quality, whether tracking flows back into your store correctly.

This is the whole point of the overlap. You're getting real production data on the new provider while your revenue is still protected by the old one.

Step 4: Shift the bulk over

If step 3 went well, move the remaining inventory. Time this deliberately: pick your slowest sales week of the quarter, never a promotional period, and never in Q4 if you're a seasonal seller. Let the old warehouse draw down naturally where you can, so you're moving less physical stock.

Step 5: Close out the old account properly

Confirm final counts, reconcile the last invoice, retrieve anything left behind (returned items often sit unnoticed), and get written confirmation the account is closed. Keep the final inventory report — you'll want it if a discrepancy surfaces later.

The details that actually cause problems

• In-flight orders. Agree explicitly on a cutoff: orders placed before time X are fulfilled by the old warehouse, after X by the new one. Ambiguity here produces both double-shipments and unshipped orders.
• Returns addressed to the old warehouse. Customers will keep sending returns to the old address for months, because it's printed on packing slips already in the wild. Arrange forwarding, and update your return address everywhere before cutover.
• Inventory sync. During the overlap, your store is pulling stock levels from two sources. Make sure your platform reflects combined availability, or you'll oversell.
• Tracking data. Confirm tracking numbers actually write back to your store and trigger customer notifications. Test with a real order before you rely on it.
• Freight between warehouses. If you're moving stock directly from old to new, palletize it properly. Loose cartons cost more to receive on the other end.

How long it should take

For a small-to-mid Shopify brand, a comfortable migration runs three to six weeks end to end — about a week to onboard and integrate, two to three weeks of overlap while you validate, and a week or so to move the bulk and close out.

You can compress it to under two weeks if you have to. You shouldn't, unless something is actively going wrong at your current provider. The overlap period is the part that makes this safe, and it's the first thing people cut.

Questions to ask a prospective 3PL about migration

• Will you receive inventory transferred directly from another 3PL, and what does that receiving cost?
• Can we run split fulfillment during a transition, or do you require all inventory before going live?
• How long does store integration take, and is there a setup fee?
• What's your standard order turnaround, and what happens during peak?
• Who is my actual point of contact, and how fast do they respond?
• Is there a minimum volume or minimum monthly spend?

The answers matter, but so does how they're delivered. A provider who gives you clear, specific numbers on migration questions is showing you how they'll communicate once you're a client. One who deflects into vague reassurance is showing you that too.