How to audit a 3PL invoice: a step-by-step checklist

Why audit a 3PL invoice, even with a good 3PL#

Errors on 3PL invoices tend to come from process, not bad faith, so a careful 3PL can still bill the wrong amount. Guides written for 3PLs list causes such as outdated rate cards, manual data entry, unit-of-measure mismatches and undocumented special projects^4,5. In the invoices we review, rates change more often than brands expect, sometimes one line at a time, and the rate in the 3PL's billing system can lag the rate card.

The invoice is built from the 3PL's own activity data³, and an audit compares it with yours. Errors also run the other way: some billable work is never entered, so it never reaches the invoice⁶. Tell your 3PL you're starting a regular invoice review and ask for the detail files to come with every invoice. A good 3PL will welcome it, and asking up front is easier than asking during a dispute.

Before you start: what you need#

You need three sets of records: what you agreed (the contract and rate card), what you were billed (every invoice and its detail), and what happened (your own order, receiving and inventory data). This adapts the accounts-payable three-way match, which checks an invoice against the purchase order and receiving record⁹; the contract stands in for the purchase order⁸.

B2B brands add bills of lading and freight (LTL/FTL) invoices; brands shipping on their own carrier account add the carrier's invoices. Invoices arrive as PDFs, spreadsheets, portal exports or EDI (the 810 invoice, or the 210 for motor carrier freight)^11,12. A 3PL's billing system can list each billable event and how it was charged³. If detail files don't come with your invoices, ask for them; see The supporting detail files you should always request.

How to audit a 3PL invoice, step by step#

The steps below follow the order of a typical rate card and leave the minimum until the fees it depends on have been checked. If time is short, start with shipping, then the largest warehouse lines. Steps 2 to 8 rest on two lines of arithmetic:

Step 1. Collect every invoice for the period and check the totals#

Count the invoices against the billing cycle, including separate shipping, freight, storage and returns invoices and credit notes. On weekly billing, one missing week leaves a month that looks plausible but is incomplete.

In the invoices we review, the same month's storage sometimes appears on more than one invoice after a correction, reissue or split. Ask the 3PL to mark each corrected or reissued invoice with the number of the invoice it replaces, and treat an unmarked second invoice for the same period as a question, not a duplicate or an addition.

Then tie out the numbers: line items sum to the summary, each line's quantity × rate equals its amount, and each detail-file total equals its invoice line. Check which lines any tax line is calculated on and that tax isn't also inside the line amounts.

The PDF and the detail file can disagree. Causes include a detail file for a different invoice or period, tax shown on one document but not the other, flat fees, shortfalls or manual charges with no detail rows, prior-period adjustments or credits included in only one, and a corrected or split invoice. Neither wins by default: list both totals, find the lines that make up the gap, and ask the 3PL which is final and to reissue so they agree before you approve payment. See Anatomy of a 3PL invoice: summary, line items and supporting detail and Separate invoices for fulfillment, storage, shipping and freight: tying them together.

Step 2. Check every rate against the rate card in effect#

Map each invoice line to the rate card line with the same unit (per order, unit, pallet or hour)^2,13. Check its rate against the card version that applies to the period. Where one line combines fees (a "fulfillment" line can include picks, packaging or the shipping label), split it using the detail file. Any line without a matching rate card line or unit goes on a question list for Step 7¹³.

Check which date your contract uses to start a new rate, and if it doesn't say, get the 3PL's answer in writing. For orders, receipts and returns, a new rate usually applies to work done on or after its effective date; for storage, to the storage period or count date that starts after it; for monthly fees, from the next month. When a billing period straddles a change, the invoice should show the quantity at each rate, as two lines or a split on one.

Check the first invoice covering work after a rate change's effective date line by line, since a change can reach one line and miss the next (Outdated rates after a contract change).

An invoice usually shows the rate applied, not the tier, so check any volume tier against the contract and your volume. With more than one warehouse, use the card for the site that did the work. See Rate verification: checking every billed rate against your rate card.

Step 3. Check receiving against what arrived#

Compare billed pallets, cartons, units, containers or hours with your POs, inbound ASNs and receipt records for the same dates⁸. Match each line to its own unit, since one contract can price receiving several ways.

A floor-loaded container takes more labor than a palletized one, so it costs more on hourly or per-carton pricing, and some cards add a surcharge for a shipment without an accurate ASN. Check those charges against what arrived and the ASN you sent, and confirm any appointment or no-show penalty against the event. See Matching billed receipts to actual receipts.

Step 4. Check storage against inventory on hand#

Compare billed storage with an inventory snapshot taken on the date, and in the way, your contract counts it. First confirm the unit: pallet position, bin or shelf, cubic foot, square foot or location; pallets and bins can appear on the same invoice. Units on hand don't give a pallet, bin or location count, so check those against the 3PL's storage report by location.

Count methods vary: a snapshot on a set day, a daily average, a peak, proration by the day or half month, or a charge at receipt for the first period plus each period after. Ask which day the 3PL counts and whether it averages. Under per-location or per-pallet pricing, a SKU with stock in a pick location and in reserve is billed for each occupied location.

On cubic-foot billing, check the item dimensions in the 3PL's system; they are more often too large than too small, and the error repeats monthly until fixed. In about a quarter of Implentio customers' 3PL contracts with storage fees, at least one storage line shows only a dollar amount. Ask for the report behind any such line. See Verifying storage counts against inventory snapshots and How storage is measured: snapshot, average, peak or billing-day count.

Step 5. Check orders, picks, packaging and returns against your orders#

Compare billed orders with the orders you shipped, looking for cancelled, duplicate or unshipped orders. Check split shipments: a true split (fulfilled across days or warehouses) customarily carries an order fee on each part, but a multi-parcel order (packed in two or more boxes at once) is one order with one order fee. If an order was cancelled after picking started, check whether your contract allows an order cancellation fee, a different charge from the order fee. Then check picks under the structure your contract uses (both are common):

These counts assume picks are counted per unit; some contracts count order lines or SKUs instead. The order fee may be labeled "first pick", and bundles or kits can be billed per component. Packaging may be billed per box or mailer, as a flat fee, rebilled at cost or cost plus, or included in the order fee. Disputes often come from scope rather than price: extra picks, inserts or kitting charged twice, and returns sorted into a higher-priced category. Check billed returns and their categories against your returns records. See Matching billed orders to shipped orders and Per-order fees, first-pick vs. additional-pick, and per-unit pricing.

Step 6. Check shipping charges#

Start by confirming how postage reaches you. For most DTC brands shipping on the 3PL's carrier accounts, postage is the largest part of 3PL spend. Small-parcel postage is on the 3PL's invoice in about nine in ten of Implentio customers' 3PL contracts, and many 3PL invoices label it "freight".

Then check surcharges, duplicate or voided shipping labels, and billed weight and dimensions against your product data, keeping the dimensions the 3PL declared separate from those the carrier measured. Most 3PLs pass carrier adjustments through on a later invoice, as separate lines or folded into regular shipping lines; some brands see none. See Verifying shipping markup against your contract and DIM weight audits: catching wrong boxes and wrong dims; for the three billing bases, How 3PLs bill shipping: pass-through, markup or the 3PL's own rate card.

Step 7. Check manual, one-off and accessorial lines#

Every line you can't trace to an order, receipt or storage count needs an approval, a definition or a log behind it. On a 3PL rate card, an accessorial is a charge for warehouse work outside the standard flow (carriers use the word for shipping surcharges).

Special projects can be billed hourly, per unit, or as a lump sum per project. Each needs a work order, an hours or units log, and your approval where the contract's approval rule requires it^2,8; if the contract sets no rule, ask for one. Where the card prices roles separately, check each hourly rate against the role that did the work. Check hours against the minimum billing increment; overtime may carry its own rate or a premium, and a lump sum also needs the quote behind it.

Lines labeled "misc" or "other" need a written definition before you accept them. Watch for a recurring charge with a one-time name, such as an integration fee billed every month, and resolve the question list from Step 2. See Checking manual and one-off line items and Fees you should never accept without definition.

Step 8. Check the minimum, fixed fees and tiers#

Check the monthly minimum after correcting the fees it counts, because the shortfall depends on them:

Count only the fees the clause names: fulfillment (order, pick and pack) fees only, all warehouse fees, or warehouse fees plus postage. Check for a shortfall billed when activity cleared the floor, the wrong fees counted, a shortfall during a waived ramp, a shortfall charged twice, or no calculation shown.

In a month under the minimum, a credit on a fee that counts toward the minimum (for an earlier billing error or a missed service-level agreement, or SLA) that is applied before the shortfall is calculated raises the shortfall by the same amount, so the credit is worth nothing. Unless the contract sets the order, ask for such credits to be applied after the shortfall is calculated.

A shortfall (or true-up) line appears only in months you fall short, so its absence doesn't mean you have no minimum. Confirm a monthly account or technology fee is billed once, at the contract amount (a per-order technology fee follows corrected order counts), and recheck tiers that depend on corrected volume. See Verifying minimum-billing calculations and Monthly minimums: how they're calculated, when they apply, how to negotiate them.

Step 9. Log every variance and sort it#

Record each variance with its evidence, and sort it before you dispute anything. Log the invoice and line, the billed and expected amounts, the difference, your source record and a status:

• Overcharge: billed above what the contract and your records support.
• Undercharge: billed below it, such as fewer picks billed than units shipped.
• Legitimate item outside your order data: a manual insert, an approved project, a free case.
• Question: no evidence either way yet, such as project hours with no approval on file.

We see undercharges as well as overcharges in the invoices we review, so log both with the same evidence (the FAQ covers what to do with undercharges). Check that credits promised for earlier disputes have appeared. See Not every variance is an overcharge: undercharges, manual items and special projects and Building an audit trail your finance team can rely on.

Step 10. Dispute within the window and fix the cause#

Send disputes in writing, with your log's line-level evidence and calculation, before the contract's dispute window closes. A 30-day dispute window is common; 14 days is short. The window usually starts when the invoice carrying the charge lands; check what your contract says. Where a contract adopts them, the International Warehouse Logistics Association (IWLA) standard contract terms for merchandise warehouses (revised January 2026) require disputes "in writing within 30 days from date of invoice"¹. Miss the window and you can lose the credit, however valid the error⁸.

Ask for a fix for the cause, not only a credit, and check the next invoice for the same line⁸. A wrong rate needs the rate table updated; a scope, quantity, category or mapping error needs the billing rule fixed. A good 3PL answers with the contract reference, its calculation and the data behind it⁵. See How to dispute a 3PL invoice: process and etiquette and Invoice dispute windows: why 30 days can cost you thousands.

What a clean audit looks like#

There's no reliable public benchmark for how often 3PL invoices contain errors, so judge an audit by its markers rather than by a target error rate:

• Every invoice line maps to the rate card line or lines and unit behind it.
• Every quantity traces to a detail file and to your own records.
• The first invoice covering work after each rate change's effective date is checked line by line.
• Each variance is logged with its evidence and its direction.
• Disputes go out inside the window, in writing.
• The same error doesn't come back the next month.

The invoice should show the quantity and unit behind each charge, with "enough detail to reproduce each major charge using the rate card and source transactions," in one 3PL contract consultancy's words². The US Federal Acquisition Regulation (as of September 2026) requires a proper invoice on federal contracts to show the description, quantity, unit of measure, unit price and extended price¹⁰. It doesn't govern 3PL contracts, but it shows what a checkable line carries.