How to verify 3PL storage charges against inventory snapshots

Why storage counts are worth checking#

Storage is worth checking because it bills every month whether or not you ship, and a wrong count repeats until someone catches it. Among those recurring charges, storage is one of the largest and a common place for billing errors: rates that drift above contract, counts that don't match your inventory, and inflated product dimensions.

Count errors can come from system set-up and process rather than intent, such as stale product dims or a status code that leaves quarantined stock in the general count. For where this quantity check fits in a full audit, see How to audit a 3PL invoice, step by step.

What you need before you start#

You need the contract's storage terms and three reports from the 3PL.

• Storage detail: the quantity behind the invoice line, by location, with location type and rate.
• Inventory snapshot: on-hand by SKU and storage location on the count date, with location ID and type, quantity and unit of measure, status, and lot or expiry. An averaged or peak count needs every day's snapshot. A location report run after the count date shows later stock, so ask for the one the bill used.
• Receipts and adjustments for the period.

For pallet, bin or location billing, a SKU-level on-hand report, including your own ERP's, can't verify storage because it has no locations. See The supporting detail files you should always request.

If your 3PL bills storage per location or per pallet position, its system already knows which locations it counted, so asking for that list is a reasonable request. Public companies file some of their contracts with the U.S. Securities and Exchange Commission (SEC), which publishes them, so a few 3PL contracts can be read in full. One of them, a 2016 warehouse contract, gives the brand view-only access to the 3PL's order management system⁷. Other 3PLs send the report on request, and some billing systems can't break storage down below the invoice line; then agree in writing which detail comes with each invoice. See also Audit rights: your right to inspect billing and inventory records.

Which count feeds which invoice#

Match the snapshot date to the invoice period before comparing anything, because the same month's storage line can come from different count dates. As of October 2026, one warehouse management system (WMS), per its documentation, counts inventory at the end of each billing period and bills the period ahead¹. Pallets in stock on January 31 are invoiced for February¹. One 3PL, per its help center, counts pallets on the first business day of each month and bills that month⁵. IWLA's standard terms for merchandise warehouses (2026 revision) charge a full month for goods in storage on the 1st⁶.

So a February invoice can rest on a January 31 count or a February count. Read the invoice period, find the count date in the contract, and pull that date's snapshot. Other methods need other data:

• Daily average or peak: a snapshot for each day, averaged or the highest taken.
• Any-point occupancy: one WMS bills a location for a day, week or month if it held stock at any point in it⁴, so you need location movement history.
• Receipt-date schedules: one WMS can bill from each receipt's own date³, so work from the receipts report.

See How storage is measured: snapshot, average, peak or billing-day count and Billing cycles: weekly, semi-monthly and monthly, and what's billed when.

How to rebuild the billed quantity, unit by unit#

Rebuild the quantity with the rule for your contract's unit, then compare it with the invoice line by line. If the contract bills more than one unit, such as pallets for reserve and bins for pick faces, rebuild each separately.

Per pallet position#

Under a snapshot, count the pallet locations holding stock on the count date:

Where one location ID holds several pallets, such as a floor-stacked lane, count pallets rather than location IDs. A pallet position, one pallet-sized slot, bills in full however full the pallet is, unless the contract has a half-pallet rate (see Partial pallets and rounding: how 3PLs count a "pallet"). An over-height pallet can bill as two positions⁷, at a tall-pallet rate or per cubic foot⁸.

Under a snapshot of occupied locations, a location with nothing in it on the count date shouldn't be billed. Two contract terms change that: a method that bills any location that held stock at some point in the period, and locations reserved for you, such as dedicated pick faces, that bill whether or not they hold stock. If neither applies, list the empty locations for your 3PL. See Storage billed on pallets or bins that don't exist.

Per bin or shelf#

Count occupied bins and shelves on the count date, by size tier where the rate card prices tiers separately. A bin billed as large that the snapshot shows as medium belongs in the rate check; see Rate verification: checking every billed rate against your rate card.

Per cubic foot#

Cubic-foot storage almost always bills WMS dims times quantity on hand, not location size:

Apply any per-SKU minimum: each SKU bills the greater of its cubic charge or the minimum. Check that the snapshot's unit of measure (each or case) matches the unit the dims describe. WMS dims are more often too large than too small, and a wrong dim bills every month until fixed. Ask for the dims your 3PL bills on; see Why accurate product weights and dims drive everything downstream.

Per square foot or per location#

Square-foot storage bills an allocated area, full or not, so check the billed area against the contracted area, not a snapshot; quoted square footage often includes aisles. For per-location pricing, count occupied locations by type and multiply each count by that type's rate⁴.

Daily average, peak, occupancy, proration and receipt charges#

Time-based methods need daily data or the receipts report:

One 2016 contract sets storage locations at "the average number of storage locations utilized during a given month"⁷. Under any-point occupancy, the charge is the rate × occupied days, weeks or months⁴. Price each prorated or initial (receipt) charge at quantity × rate × the fraction the contract uses. That can be days in stock, from receipt to departure⁷, receipt week⁵, half month^1,6 or a full period⁸. Aged-inventory surcharges also need receipt dates; see Long-term storage surcharges and aged-inventory fees.

Initial storage covers a receipt's first period, and recurring storage starts with the next one. If the same pallets appear on both lines for the same period, ask your 3PL why, unless your contract says the receipt charge is added on top of that period's count. Check how the contract treats stock received on the count day itself.

Why a correct bill can still exceed what your inventory needs#

A correct storage bill can show more locations than your units seem to need, because stock is stored and billed by location, not by volume alone. Check for these first:

• Pick plus reserve. A SKU can hold stock in a pick location and in reserve at once, and each occupied location bills. Each occupied location bills at its own location type's rate, so a bin pick face appears on the bin line, not as a pallet position.
• Lots and expiry dates. Where each lot or expiry date gets its own pick location, one SKU with three live lots can take three locations.
• One SKU per location. Many ecommerce 3PLs require it, so a mixed pallet is broken down or billed per SKU.
• Partial pallets from separate receipts stay separate unless consolidated, which is often negotiable and sometimes carries a labor charge.
• Status storage. About 30% of Implentio customers' 3PL contracts with storage charges also bill quarantine, returns, dock overstay or overflow storage separately; such stock shouldn't also be in the general count (see Damaged, quarantined, on-hold and non-sellable inventory).

Then run a sanity check on your on-hand by SKU:

Add the extra locations the rules above explain. A remaining gap is a question for your 3PL, not a confirmed overcharge; undercharges happen too (Not every variance is an overcharge: undercharges, manual items and special projects).

What good looks like#

Good storage billing lets you rebuild the line from the 3PL's own reports:

• The storage detail adds up to the invoice quantity, by location and location type.
• Every billed location appears in the snapshot for the stated count date.
• The contract states the unit, count method, count day, and which period each count bills.
• Status storage appears on its own labeled line.
• The 3PL answers count questions with location IDs.