How to Choose and Migrate to a 3PL: Costs, SLAs, Prep Requirements, and a 90-Day Cutover Plan for Shopify Stores

If your living room has turned into a packing station or your team is spending more time taping boxes than growing the brand, it is time to consider a 3PL. The right partner will cut fulfillment costs, speed up shipping, and stop operational fires from burning your launch momentum. The wrong one will create delays, angry customers, and expensive contract exits. This guide shows you exactly how to choose and migrate to a 3PL for your Shopify store, including cost anatomy, nonnegotiable SLAs, inbound prep, and a detailed 90-day cutover plan.

For a broader framework on choosing fulfillment partners, see the complementary checklist in Choosing the Right Fulfillment Partner and build your operational foundations alongside our Ultimate Shopify Set-Up Guide.

Why and when to move to a 3PL

You know you have reached the 3PL threshold when order volume swings are creating late shipments, your storage footprint is growing faster than revenue, or you need multi-warehouse coverage to enable 2 to 3 day delivery. The 3PL category is mature and competitive, which helps you negotiate. The market size data from Armstrong & Associates shows global 3PL revenues exceeding one trillion dollars, and the U.S. 3PL market estimates break out specialized segments like value-added warehousing and distribution. Competition means you can require clear SLAs, transparent pricing, and integration support for Shopify.

For stores using dropshipping as a validation step, our beginner’s guide to dropshipping and playbook on avoiding dropshipping pitfalls can help you decide whether a 3PL makes sense once a product line shows traction.

The cost anatomy of a 3PL

Do not sign a contract until you have a line-by-line understanding of fees. Transparent pricing is a good proxy for operational maturity. As a reference point, ShipBob’s pricing overview explains common fee categories, and the 2025 Red Stag Fulfillment pricing guide provides typical ranges across storage, picking, and projects.

• Receiving. You will see per hour or per pallet fees to unload, count, and put away inventory. Complex receiving like pallet reconfiguration or relabeling adds project fees.

• Storage. Most 3PLs charge per pallet, bin, shelf, or cubic foot monthly. The Red Stag guide notes average pallet storage in the 15 to 40 dollar range monthly, often converting to a per cubic foot metric for small items.

• Pick and pack. Pricing usually includes a base pick for the first item and incremental charges per additional item. Kitting or custom packaging is additional.

• Packaging materials. Standard mailers or boxes are sometimes included. Custom branded packaging, dunnage, or inserts are billed per order or per unit.

• Shipping labels. Carriers bill by weight or dimensional weight. The UPS guidance on dimensional weight defines the formula as length times width times height divided by a DIM divisor. Your 3PL should optimize cartonization to reduce DIM charges.

• Returns processing. Expect a per return fee plus any restocking or refurbishment charge.

• Account management. Some providers include a dedicated manager at certain volume tiers. Others charge a monthly management retainer.

• Projects and value-added services. Carton relabels, quality inspections, FBA prep, or lot segregation are scoped as hourly or fixed projects.

The most common source of unpleasant surprises is misaligned dimensions or missing carton data, which leads to unexpected DIM-based shipping costs. Get ahead of this by confirming measurement standards and the DIM divisor used across your primary carriers. The tutorial on dimensional pricing from ShipBob outlines how different carriers apply this.

SLAs that protect your customer experience

A 3PL is an extension of your brand. Bake the following SLAs into your contract with financial credits for misses. Industry commentary from Red Stag on 3PL performance metrics and this guide on keeping 3PL services high provide realistic targets.

• Order accuracy. Aim for 99.5 percent or higher. Red Stag positions 99 percent plus as a baseline for reliability.

• Same day ship rate. For orders in by the cutoff, expect 95 to 99 percent same day ship. The FCBco analysis cites that many brands target that range, with caveats during volume spikes.

• Cutoff times. Set a clear daily cutoff per node. Ask for peak season adjustments.

• Dock to stock time. For inbound receiving, 24 to 48 hours is common, which aligns with the FCBco guidance on typical targets.

• Inventory accuracy. Negotiate 98 to 99.9 percent by cycle count. Clarify how shrinkage is handled and capped.

• On time shipping. Define the percentage of labels tendered to carriers on time and how carrier outages are escalated.

• Support SLAs. Define response and resolution times for ticket priority levels.

SLAs only matter if you can measure them. Require weekly scorecards with order accuracy, same day ship, dock to stock, inventory variance, and carrier performance. Include a quarterly business review that maps operational metrics to your growth plans. For proactive scaling tips beyond ops, bookmark our guide on overcoming growing pains.

Prep and compliance: what your 3PL needs from you

A smooth start hinges on crisp product data and standardized packaging. Shopify’s core documentation on using SKUs explains why unique SKUs per variant are essential for inventory integrity. For barcodes on products, Shopify’s barcode overview points sellers to GS1 best practices.

For cases and pallets, many 3PLs require GS1-128 carton labels and advanced shipment notifications. The GS1 Logistic Label Guideline details how SSCC identifiers and barcodes should appear on cartons and pallets. For an approachable overview, the SPS Commerce explainer on UCC-128 labels breaks down data elements and use cases.

Create a single source of truth with the following fields per SKU: dimensions and weight, acceptable box sizes, inner and master carton quantities, retail barcode if applicable, BOMs for kitted items, and any lot or expiry attributes. Share unboxing photos, packaging diagrams, and a cartonization matrix so the 3PL can optimize pick paths and reduce freight costs. If you are investing in automation, our guide to workflow automation for eCom shows how to connect order flags, fraud checks, and fulfillment routing rules.

Shopify setup for a 3PL migration

Shopify makes it straightforward to route orders to a 3PL and keep inventory accurate across locations. The Shopify Help Center on fulfillment options outlines your choices, from self-fulfillment to third-party providers. In practice you will configure three areas.

1. Locations. Add each 3PL warehouse as a location so Shopify can track stock by node. The Locations documentation covers how to create locations and set priorities.

2. Fulfillment service connection. If your 3PL integrates directly, they will register a fulfillment service and sync via the FulfillmentService resource. The Shopify developer docs for FulfillmentService and FulfillmentOrder explain how third parties claim and fulfill items from specific locations. If you are using a manual or email-based flow, the Custom fulfillment services setup lets you add a provider and automatically email packing lists when orders are tagged for that service.

3. Inventory transfers. Use Shopify transfers to send stock to the 3PL and receive it into the new location. The inventory transfers guide shows how to create and receive shipments, which keeps in-transit and on-hand quantities correct.

Before go live, perform SKU mapping verification between Shopify and the 3PL WMS, confirm tax and shipping profiles, and test the full flow from checkout to shipment. If you are launching your store alongside the 3PL search, you can start at Shopify and build your checkout foundation quickly.

A 90-day cutover plan that works

Day 0 to 30: Selection and scoping

Start with a short RFP that defines your SKU count, monthly order profile, seasonality, channels, special handling, and international needs. Ask for references in your product category, quote templates with the fee structure, and tech diagrams. Schedule virtual site tours and a pilot pack test with 20 to 50 orders. Lock the SLA schedule, include credits for misses, and attach an exit plan.

In parallel, audit product data. Ensure every variant has a unique SKU, accurate dimensions and weights, and barcode assignments that match your packaging. Verify that bundles and kits are represented either as pre-kitted SKUs or as a WMS kit of materials. For paid social traffic surges that will hit ops later, tighten acquisition with our guide to high-converting social ads so you feed the 3PL predictable demand.

Day 31 to 60: Onboarding and receiving

Connect the 3PL integration in Shopify and add new locations. Create routing rules by location priority so orders route to the closest stocked node. Share your cartonization matrix and test rates for your top 20 items.

Prepare inbound with carton and pallet labels aligned to GS1-128 where required. Include a digital ASN with SKU, quantities, and lot or expiry data if relevant. Agree on dock to stock SLA, typically 24 to 48 hours as noted by FCBco’s SLA guidance. Use Shopify transfers to move inventory into the 3PL location so on-hand quantities match what the WMS will show.

During this phase, run full end-to-end tests. Place test orders for each shipping service level, verify pick accuracy, measure label rates, and confirm tracking flows back to Shopify. Validate returns workflows and disposition rules. Add alerting for exceptions, for example unscannable barcodes or address validation fails.

Day 61 to 90: Parallel run and go live

Begin a parallel run where the 3PL fulfills a slice of your live orders while your existing setup handles the rest. Use clear tags or shipping profiles in Shopify to split traffic by channel or region. Monitor your weekly scorecard for same day ship rate, order accuracy, and inventory variances. Investigate every miss.

When confidence is high, set the 3PL locations to priority in Shopify so new orders route there first. Keep a safety stock buffer at your prior location for 7 to 14 days in case of surprises. After cutover, deprecate the old location and update customer communications templates to reflect new shipping speeds and tracking links. To capitalize on faster delivery, tighten retention with our playbook on building an email marketing campaign that converts.

Questions to vet your 3PL shortlist

• Which WMS do you run, and how do you integrate with Shopify Fulfillment Orders? Ask for a diagram and API call log samples.

• What are your average and peak same day ship rates and order accuracy for stores like ours? Request a blinded KPI report.

• How do you handle DIM optimization and cartonization to reduce shipping costs? Share your carton library and rules.

• What is your standard dock to stock time and process for ASNs? Confirm receiving fees and SLA credits.

• How do you process returns and update disposition in Shopify? Show the flow for resellable, damaged, and refurbishment.

• What is your inventory accuracy commitment, cycle count cadence, and shrink policy? Define thresholds and credits.

• How do you staff for Q4 and major promotions? Provide a peak readiness plan and change freeze policy.

• What is the exit process and data handback if we decide to move? Require a defined offboarding checklist.

Avoidable pitfalls during migration

Most 3PL migrations stumble on the basics. Missing or duplicate SKUs confuse routing and inventory synchronization. Inaccurate dimensions lead to unexpected shipping label costs because of DIM weight. Unlabeled cartons stall receiving. Solve these by running a SKU audit, adopting GS1 barcode standards, and piloting a small batch before the main inbound. If you are also reworking internal processes, our guide to automation for eCom operators shows how to add order tagging, routing logic, and exception alerts without heavy engineering.

Shopify’s configuration deserves similar attention. Confirm that each fulfillment location has the correct inventory, shipping zones, and service levels. Use test orders to validate tax, shipping, and tracking events. The Shopify custom fulfillment service setup is a fast failsafe if your provider cannot complete a full API integration on your timeline.

Finally, get your demand plan right. Surprising your 3PL with an unannounced campaign or influencer drop is the fastest way to miss SLAs. Share a rolling 8 week forecast and precise marketing calendars. If your growth plan includes new channels, the eComAmplify library covers acquisition and operations from SEO basics for e-commerce to social ads, all tailored for Shopify operators.

Quick reference: your migration checklist

• Define requirements. Order profile, SKU count, handling rules, growth plan, international.

• Shortlist and RFP. Pricing template, SLAs with credits, tech integration diagram, references.

• Contract. Term, SLA schedule, exit plan, data handback, rate increase caps.

• Data hygiene. Unique SKUs, accurate dimensions and weights, barcodes, bundle logic.

• Shopify setup. Locations, service connection, routing rules, test orders, transfers.

• Inbound readiness. GS1-128 carton labels, ASN data, dock appointment, receiving checklist.

• Parallel run. Split traffic, scorecard reviews, exception management, safety stock.

• Cutover. Location priority switch, communications update, deprecate old node, QBR cadence.

If you are still evaluating platforms or setting up your first store, spin up a trial at Shopify, then follow our zero to live store guide to get your catalog, payments, and shipping rules dialed before engaging 3PLs.