3PL WMS: What to Ask About a Warehouse Management System Before You Sign

A 3PL's warehouse management system (WMS) is the software that records every unit of your stock from the moment it arrives to the moment it leaves. Before you sign, ask what the WMS tracks, what you can see in the client portal, how often stock syncs to your sales channels, how accuracy is measured and how you get your data out if you leave. Those answers show how the day-to-day service will run.

The questions below run in the order you meet them, from receiving to exit, and sit alongside our pillar guide on how to choose a 3PL for your ecommerce brand.

The pain points

• Shopify shows stock we don't have, and we keep overselling at the weekend.

• I have to email the account manager to find out whether our delivery has been booked in.

• Every report I need arrives as a spreadsheet on a Monday, already out of date.

• We asked for a free sample in every first order and were told it needs a development ticket.

• I've no idea what happens to our order history if we move warehouses.

What the WMS does for your brand

Every 3PL runs some kind of WMS. What varies is how much of your operation it records and how much you can see. At a minimum it should cover:

• Receiving: checking each delivery against what you said was coming, by SKU and quantity, and recording any shortfall or damage.

• Putaway and stock by location: every unit sits in a known bin, so a picker walks straight to it.

• Pick and pack: orders are grouped into pick runs and scanned at packing, so a wrong item is caught before it ships.

• Batch, expiry and serial numbers: needed for food, supplements, cosmetics and electronics. Ask whether it picks first-expiry-first-out and can trace a batch to the exact orders it went into.

• Returns: booking returns in, grading their condition and putting sellable units back into available stock.

Ask to see each step on a live client account in a demo, with names hidden.

The client portal: what you should see without asking

The portal is the part of the WMS you use. A good one answers routine questions without an email. Look for:

• Live stock by SKU, split into available, allocated to orders, damaged and quarantined.

• Order status from received to dispatched, with tracking numbers.

• Inbound bookings, where you raise an advance shipping notice (ASN) and follow each delivery through to putaway.

• Returns logged with a reason and a condition grade.

• Reports you can run and export yourself, filtered by date, SKU and channel.

• Separate user logins with permissions for your ops team, finance and customer service.

Ask for a demo login before you sign and try to answer your most common questions yourself. If you can't find the answers, your team won't either.

Integrations and how often stock syncs

Orders flow into the WMS, and stock and tracking flow back to every place you sell. Ask how each connects:

• Shopify and other web platforms: a native app or a connector, and who maintains it when the platform changes. Our guide to Shopify 3PL integration covers the set-up.

• Marketplaces: Amazon, eBay, TikTok Shop and others, directly or through your multichannel tool.

• ERP or accounting: whether stock movements and dispatches can feed your ERP.

• API: whether there is a documented API your developer can use, and whether calls are limited or charged.

• EDI for retailers: if you supply retailers that order by EDI, whether the 3PL handles EDI purchase orders and dispatch notes itself or you need a separate EDI provider.

Then ask how often stock syncs to each channel. Some connections push a change the moment it happens. Others run on a schedule. A slow sync is where overselling starts: a unit sells on one channel and still shows as available on another. Get each channel's sync frequency in writing, and ask who is alerted when a connection fails.

Stock accuracy and how it is measured

Ask every 3PL how it measures stock accuracy.

• Cycle counts: how often your SKUs are counted, whether fast-moving or high-value lines are counted more often, and whether you see the results in the portal.

• The accuracy method: whether it is measured by units, by SKU or by bin location. A figure worked out one way can't be compared with one worked out another way.

• Adjustments: every stock adjustment should appear in the portal with a reason code, a date and the user who made it.

• Liability: who pays for stock losses above an agreed tolerance.

No single benchmark applies to every 3PL, so agree the method and the target in the contract, and ask for a sample adjustment report with client names removed.

Your data, reporting and exit

Your order history, stock movements and customer addresses live in the 3PL's system. The contract should say you own that data and can export it at any time, in a standard format such as CSV.

Customer names and addresses are personal data. Where the 3PL processes them on your behalf, UK GDPR requires the contract to say that at the end of the service it will delete or return all of that data at your choice, and delete any remaining copies unless UK law requires it to keep them. The ICO sets this out in its guidance on what a controller and processor contract must include. Read it next to our guide to 3PL contract terms.

For exit, agree a full stock report by SKU, batch and location, plus order and returns history, within a set number of days of notice. The physical move is covered in our guide to moving stock between 3PLs.

Multi-site, custom rules and support

These decide whether the WMS keeps up as you grow.

• Multi-site: if the 3PL runs more than one warehouse, whether one portal shows stock across all sites and whether orders route to the site holding the stock.

• Custom rules: kitting and bundles, inserts and free samples, gift messages, and channel-specific packing such as retailer labelling or branded boxes for web orders only. Ask which are standard settings and which need development work.

• Change requests: how you raise one, the usual turnaround and whether it is charged.

• Uptime: the uptime commitment and what happens to picking if the system goes down.

• Support: support hours, including weekends and peak.

What to ask a 3PL

• Can you show me receiving, picking, packing and returns for a live client in the WMS?

• How does each of my sales channels connect, and who maintains each connector?

• How often does stock sync to each channel, and what happens when a sync fails?

• How do you measure stock accuracy, and how often will my SKUs be cycle counted?

• Can I export all my data myself, and in what format?

• What data do I receive at exit, and within how many days?

• Which of my packing rules are standard settings, and which are charged change requests?

• What uptime do you commit to, and what are your support hours in peak?

Our recommendation: test the portal before you sign

1. List your sales channels, SKU count and any batch, expiry or serial number needs.

2. Write down the five questions you ask your current provider most often.

3. Ask each shortlisted 3PL for a demo login and try to answer those five questions yourself.

4. Get the sync frequency per channel, the accuracy method and the adjustment reporting in writing.

5. Send your list of custom packing rules and ask which are standard and which are charged.

6. Put data ownership, export format and exit deliverables into the contract.

7. Push test orders through every channel before you move the full range.

What waiting costs

A WMS gap found after go-live costs more to fix than one found in a demo. A system that oversells means cancelled orders and weaker marketplace metrics. Packing rules you assumed were standard arrive as change request invoices. Weak exit terms leave your history locked in the old system.

Take a brand with 800 marketplace orders a month whose stock syncs to the marketplace a few times a day. If 2% of those orders are oversold and cancelled, that is 16 cancelled orders a month. At an average order value of £35, the brand loses £560 in sales each month, plus about 15 minutes of customer service time per cancellation, or 4 hours a month. Over six months that is £3,360 in lost sales and 24 hours of staff time, before any marketplace penalty. These figures are made up to show the method.

People Also Ask

What is a WMS in a 3PL?

It is the software a 3PL uses to receive, store, pick, pack and dispatch your stock and record where every unit is. Brands see it through a client portal.

How often should a 3PL sync stock to Shopify?

There is no fixed standard. Some connections push changes as they happen and others run on a schedule. If you sell the same stock on several channels, a faster sync reduces overselling, so get the frequency in writing.

Who owns my data in a 3PL's warehouse management system?

That depends on your contract, so make sure it says you own your order, stock and customer data and can export it at any time. Where the 3PL handles your customers' personal data for you, UK GDPR requires the contract to cover deleting or returning it at the end of the service.

Finding the right 3PL partner

Logan, FulfilQ's advisor on the website, matches brands to verified providers by order volume, product type and region. Tell Logan your sales channels, SKU count and any batch or expiry needs, and you get a shortlist to ask about client portals, stock sync and data exports. Start at fulfilq.com and Ask Logan, or Submit an RFP and verified providers come back to you. You can also browse the full provider directory.