Inventory Not Adding Up? 10 Questions to Ask Your 3PL Before You Blame the Sales Channel

When inventory is not adding up between your 3PL and your sales channels, start with the warehouse record, not the channel. Ask your 3PL for the stock movement history, inbound receipts against pre-advice, non-sellable stock, returns, adjustments and the figure it pushes to each channel. A good 3PL answers each with data within a day.

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Channels mostly display what they are sent. When a SKU oversells, the cause usually sits in a receipt, a status, a return or a sync rule. Below are the ten questions our team would want a client to ask us, with good and worrying answers, plus a discrepancy log you can copy.

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A stock discrepancy is any difference between the quantity your systems believe is available and the quantity physically held and sellable in the warehouse. Fulfil with Synergy is a founder-led UK 3PL and growth partner for ambitious, fast-growing consumer brands, running a technology-led fulfilment centre in Northampton for health, wellness, beauty, supplement and lifestyle brands across D2C, marketplace, retail and wholesale. We answer each question below from our RedPrairie Dispatcher warehouse management system and live stock audit trail.

1. "Can you send me the full movement history for this SKU, with timestamps and who made each change?"

Every investigation starts here, because the movement history shows when the numbers diverged.

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Why ask it: A count shows the current position; the history shows whether stock left via a pick, adjustment, transfer or write-off, and when. Shopify's adjustment history logs the date, activity and who made each change, so lay the two side by side.

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A good answer sounds like: "Here's the export. Every receipt, pick, move and adjustment is time-stamped and tagged to a user, with a reason code."

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A worrying answer sounds like: "We can tell you what's on hand now, but not how it got there." If the warehouse cannot trace a movement, nobody can fix the cause.

2. "What did you receive against my pre-advice on the last three deliveries?"

Most mismatches that appear weeks later began at goods-in.

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Why ask it: If 1,200 units were advised and 1,140 arrived, but someone booked 1,200, your channels will sell 60 phantom units. Short, over and mis-labelled deliveries all need to be visible as a variance on the day they land.

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A good answer sounds like: "Here's an inbound report showing advised, received and variance per line, with photos of any damaged or short cartons."

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A worrying answer sounds like: "We just book in what's on the paperwork." That means nobody checked.

3. "How much of my stock is sitting in a non-sellable status, and why?"

On-hand and available are different numbers, and confusing them causes many oversells.

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Why ask it: Units held in quarantine, damaged, awaiting checks, short-dated or reserved for wholesale are physically there but not sellable. If your channel is fed on-hand rather than available, you will sell stock that cannot ship.

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A good answer sounds like: "Here's your stock split by status and location, with the reason each unit is held and who can release it."

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A worrying answer sounds like: "It's all in the building somewhere."

4. "When a return arrives, how long until it is back in sellable stock, and where does it go if it fails inspection?"

Returns are the quietest source of drift, because stock moves in two directions at once.

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Why ask it: A refund does not put a unit back on the shelf. Unprocessed returns mean you undersell; uninspected restocks mean you sell damaged units.

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A good answer sounds like: "Each return is graded with a reason code, then restocked, held or disposed of, and the outcome shows in your returns data." At Fulfil with Synergy, returns are processed within 48 hours of arrival.

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A worrying answer sounds like: "Returns go in a cage and we get to them when we can."

5. "When did you last count this SKU, and what adjustments came out of it?"

Counts correct the record; adjustments without reasons hide the cause.

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Why ask it: Writing off 40 missing units fixes the number, not the problem. You need the date, variance, reason code and proof someone looked for mis-slotted stock first.

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A good answer sounds like: "Last counted on this date, variance of minus 12, found 10 in a neighbouring location, two written off as damaged, both logged."

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A worrying answer sounds like: "The system adjusts automatically after counts." Automatic is fine; unexplained is not.

6. "Is my stock split across batches or locations, and is allocation following the rule we agreed?"

Stock can be correct in total and still wrong where it matters.

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Why ask it: Supplements, skincare and anything dated should be picked by FEFO (first expiry, first out) or FIFO. If a batch is blocked, expired or in a location the pick logic cannot reach, orders fail while totals look healthy.

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A good answer sounds like: "Here's every batch, expiry and location for that SKU, and FEFO is applied automatically by the WMS."

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A worrying answer sounds like: "Pickers grab whatever is nearest."

7. "What stock figure do you send to each channel, how often, and is any buffer applied?"

This is where warehouse and channel meet, so test the integration rather than assume it.

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Why ask it: Perfect stock still oversells if updates go in batches, send on-hand instead of available, or split one pool across channels. Our article on why stock levels drift apart across Amazon, Shopify and TikTok Shop covers those sync causes in full. Amazon Seller Fulfilled Prime raises the stakes: Amazon expects a cancellation rate below 0.5% and more than 99% of orders shipped on time, and every oversold order you cancel counts against you. See our guide to keeping Seller Fulfilled Prime stock accurate.

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A good answer sounds like: "We send available-to-sell from one stock pool on every movement, by API, and here are the last 24 hours of updates for that SKU."

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A worrying answer sounds like: "Your app pulls it twice a day."

8. "How do bundles and kits deduct their components?"

Bundles are the most common reason a channel shows stock the warehouse cannot build.

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Why ask it: A gift set built from three components must reduce all three on each sale. A pre-built kit deducts components at assembly, not again at despatch.

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A good answer sounds like: "Pre-built kits are a separate SKU created at assembly; virtual bundles deduct components at allocation. Here's the mapping."

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A worrying answer sounds like: "We just pick what's on the packing slip."

9. "What exceptions were raised on my account this month, and who closed each one?"

Exceptions are the warehouse's early warning system, and the log shows whether anyone acts on them.

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Why ask it: Short picks, empty locations, failed scans and unmatched returns should all raise an exception. A 3PL that cannot show you its exception list is either not recording them or not reviewing them.

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A good answer sounds like: "Here's the exception log with the cause, the action and the person who closed it, and we'll go through the patterns in our weekly review."

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A worrying answer sounds like: "We haven't had any."

10. "Who owns this investigation, and when will I get a written root cause?"

Ownership turns a complaint into a fix.

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Why ask it: Discrepancy emails bounce between account managers, supervisors and IT. You need one named person, a date and a written cause, correction and process change. Check your contract for stock loss liability and accuracy KPIs first, so you know what remedy applies.

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A good answer sounds like: "I own it. You'll have a written root cause by Thursday, and we'll review it in our weekly ops call."

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A worrying answer sounds like: "Leave it with us."

Discrepancy log: a one-page template you can copy

Keep one row per discrepancy and share it with your 3PL every week. Patterns appear within a month: the same supplier, the same SKU family or the same day of the week.

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• Example: 03/11. SKU / batch: SER-30ML / B2241. Channel qty: 140. 3PL on hand: 152. 3PL available: 128. Last audit trail movement: Moved to quarantine 31/10, user tagged. Questions asked: 1, 3. Root cause agreed: Inbound damage not flagged. Owner: Client Manager. Closed / correction: 05/11, feed switched to available.
• . .
• . .

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Record on hand and available separately, because they point to different causes. Never close a row with "adjusted" alone: the root cause is what stops it happening again.

If the answers keep coming back vague

If your 3PL cannot answer most of these questions with data, the problem is the visibility of your whole operation, and that is when brands start asking which UK fulfilment companies to consider instead. At Fulfil with Synergy, the answers are built into how the warehouse runs:

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• Audit trail: RedPrairie Dispatcher WMS tracks stock to unit, SKU, batch and location, with a time-stamped, user-tagged stock movement history.
• 24/7 client portal: live inventory, stock movements, inbound status, order status, returns data and custom reports. Our guide to what a fulfilment client portal should show you sets out the standard.
• Exception handling: short picks, failed scans and inbound variances raise exceptions in the WMS before a customer complains.
• People who own it: a named Client Manager, a Client Support Specialist on the floor and an escalation path to the Head of Operations, the COO and me, with weekly operational reviews so discrepancies are discussed while still small.
• A clean start: when a brand moves to us, goods-in discrepancies are photographed, logged and resolved jointly, and the transition ends with a formal stock reconciliation report.

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Boody's Global Fulfilment Manager, Gab Drake, said: "The UK used to be one of our most challenging regions from a fulfilment perspective." After the move: "Since moving to Fulfil with Synergy, it has become one of our top-performing markets operationally, and we're now fully equipped to scale with confidence!" Read how Boody scaled with Fulfil with Synergy.

FAQ

How do I know if the 3PL or the sales channel is causing the stock mismatch?

Compare three numbers for one SKU: what the channel shows, what your 3PL reports as on hand, and what it reports as available. If the channel matches the 3PL's available figure, the warehouse record is the source. If the channel differs from both, the integration or channel settings are at fault. Then check the audit trail for the last movement before the gap appeared, which tells you whether a receipt, return, adjustment or transfer caused it. Repeat for two or three affected SKUs before drawing a conclusion.

What is an acceptable number of stock discrepancies from a 3PL?

There is no single figure for every brand, but the target should be written into your contract as an inventory accuracy KPI, measured the same way every month. What matters as much as the rate is the response: every discrepancy should have a named owner, a root cause and a correction. Fulfil with Synergy reports performance against contracted KPIs in weekly operational reviews, so a trend is visible before it becomes a peak-season problem. If your contract has no accuracy KPI at all, add one at the next review.

Can I ask my 3PL for an independent stock count?

Yes. Most contracts allow you to request a full or partial count, though some charge for it, so check the terms first. A targeted count of the SKUs in your discrepancy log is usually faster and more useful than a full stocktake. Ask to attend or receive count sheets with locations, and compare the results against the movement history so you learn why the gap exists, not just its size. Agree in writing how any confirmed shortfall will be treated under your contract.

Should I switch 3PL if my inventory keeps not adding up?

Switch when the pattern is visibility and ownership, not a single error. If your 3PL cannot show a movement history, cannot separate on-hand from available stock, or leaves discrepancies without a written root cause, a new provider with better systems will serve you better. Before you sign anywhere, use our list of questions to ask a 3PL about real-time visibility before you sign, and ask to see the portal live. Check your notice period and stock release terms before you raise it.

How long should a 3PL take to explain a stock discrepancy?

A 3PL with a full audit trail should give you the movement history for a SKU within one working day, and a written root cause within a few working days for anything that needs a physical check. Agree the timings in your service level agreement. Longer gaps usually mean the data is not easy to pull, which is itself a warning sign. At Fulfil with Synergy, your Client Manager owns the investigation from first report to close, with updates in writing.

When inventory is not adding up between your 3PL and your channels, the answer usually sits in the warehouse record. Ask the ten questions, log every answer and judge your provider on how quickly it shows you the data. Fulfil with Synergy pairs a time-stamped audit trail and 24/7 portal with a named Client Manager who owns every discrepancy.

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If your numbers have stopped making sense, talk to the Fulfil with Synergy team about a stock reconciliation.

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