How to verify a cost-plus shipping markup against your contract

Why the shipping markup is worth checking#

A markup applied at the wrong number, or to charges the contract doesn't cover, repeats on every label it applies to. For most direct-to-consumer (DTC) brands that ship on the 3PL's carrier accounts, postage is the largest share of total 3PL spend, larger than all warehouse fees combined. Small-parcel postage sits on the 3PL's own invoice in about nine in ten of Implentio customers' 3PL contracts.

A 3PL is entitled to mark up shipping (Why 3PLs mark up shipping, and how parcel margin works). On cost-plus the markup is stated, and 3PLs that bill this way are generally fine showing it, so the check is whether each billed amount follows the written rule. Most brands get a rate card instead, with the markup built into the rates, and it's up to the brand to decide whether those rates are acceptable. This article covers parcel postage; pallet freight is billed differently (Freight (LTL/FTL) billing for B2B orders).

What your contract needs to say before you can check it#

You can check a markup only against a written rule, in the master services agreement (MSA), a statement of work, the rate card, a pricing exhibit or an email. Read its operative words first: "pass-through", "cost plus X%", "plus $X per label" and "X% off" a carrier table each call for a different check.

The clause needs to settle six things:

1. The basis for each carrier and service.
2. On cost-plus, the markup as a number, so you can validate each charge against it.
3. The charges it covers: base postage, fuel, each other surcharge (residential, delivery area, additional handling, peak or demand, address correction), later carrier adjustments and carrier credits.
4. What a flat fee counts: packages or shipments, and whether return, voided and own-account labels count.
5. What "cost" means. "Cost" should mean the net charge on the carrier's invoice for that label, after the discounts shown on it. Incentives or rebates a carrier pays a 3PL across all its shippers are a separate matter; the contract should say if they're excluded.
6. The effective date of any change (Outdated rates after a contract change).

Whether later carrier adjustments are marked up depends on the contract, and many contracts don't say. If the clause says "cost plus X%" and lists nothing, don't assume either way about fuel, other surcharges or adjustments: ask the 3PL which charges it marks up, including fuel charged on surcharges, and get the answer in writing. In the invoices we review, we sometimes see a markup on surcharges or fuel that the clause doesn't name. If no markup is written at all, there's no number to check against, only the 3PL's current practice, so ask it to confirm the basis and number in writing.

How to check each shipping basis#

Identify the shipping basis for each service first (How 3PLs bill shipping: pass-through, markup or the 3PL's own rate card). Pass-through and cost-plus are checked against carrier cost; the 3PL's own rate card is checked against the card.

Pass-through at carrier cost#

On pass-through billing, each label should cost what the carrier charged the 3PL, so the gap is zero on every carrier charge. The word is a claim: one e-commerce fulfillment contract filed with the U.S. Securities and Exchange Commission (SEC) in 2000 prices shipping at actual cost plus a percentage, yet says shipping charges "will be passed through"⁷. A separate shipping-label or processing fee may still apply (Label fees, address correction fees and reshipment charges).

Cost plus a percentage#

Check charge by charge, since the clause may leave some charges at cost:

As of October 2026, UPS and FedEx set fuel as a weekly percentage applied to transportation charges and some other surcharges^1,2; on FedEx ground services those include residential and delivery area¹. A markup on fuel stacks on top of it; ask which rule covers fuel on a surcharge the clause leaves at cost.

Cost plus a fee per label#

The billed amount should equal carrier cost plus the fee times the labels the clause counts: per package or per shipment, with or without return, voided and own-account labels (Duplicate tracking numbers and voided labels billed). It may be its own line, such as a "freight fee" (parcel postage, not pallets), and a per-label line can also pay for work rather than mark up postage.

The 3PL's own rate card#

On the 3PL's own rate card, there's no markup to measure and none needs to be in writing. If the card already has the markup built in, the only decision is whether you're happy with those rates. Check each billed price against the card version in effect for the ship date: service, zone, billable weight and surcharges (Rate verification: checking every billed rate against your rate card). Fuel, surcharges or adjustments the card passes on at the carrier's amounts are checked like pass-through. An "X% off" card is checked against the exact carrier table it names (as of October 2026, UPS daily or retail³, FedEx list or retail⁴, USPS Commercial or Retail⁵).

Your own carrier account#

The carrier bills you, so there's no 3PL markup on postage. Check any fee the 3PL charges per own-account shipment⁸, and audit the carrier's bill with How to audit carrier invoices.

How to check the markup on a sample of labels#

On cost-plus, check the stated markup against the cost behind each charge:

1. Pick the sample. Review every invoice, at the very least with a spot check; a spot check only shows order of magnitude. Spread it across services, zones, surcharge-heavy parcels and carrier adjustment lines.

2. Get the carrier cost for those tracking numbers. Ask your 3PL for the carrier cost behind each sampled label, for example as a cost column in the shipment-level file. That column is the 3PL's own record of cost, so a match with its invoice proves the markup arithmetic, not the cost itself. For USPS labels billed at pass-through or cost-plus, the postage platform's history for those labels is also an acceptable record of cost. If a 3PL billing at cost plus won't show the cost, the markup can't be checked; ask for it in writing before you renew.

3. Split each label into base postage, fuel, each surcharge and any later adjustment, on both sides, joined by tracking number.

4. Compute the markup on each component:

   Markup = (billed − carrier cost) ÷ carrier cost

   Dividing by the billed amount gives margin instead⁶.

5. Compare each component with the clause, including the charges it leaves at cost.

6. Scale any difference to the month: the difference per affected label × affected labels.

This check tests the markup arithmetic, not whether the carrier cost was right: a wrong billable weight, a wrong service or a surcharge that shouldn't apply raises cost and markup together. Check those with Billed weight vs. expected weight: finding overbilling, Surcharge audits: residential, delivery area, additional handling and Fuel surcharges on a 3PL invoice: checking the percentage, what it applies to and your contracted discount. To match a full month of carrier invoices to 3PL lines, see Reconciling carrier invoices to 3PL shipping charges.

What good looks like#

• The basis written for each carrier and service.
• On cost-plus, the markup as a number (a percentage or a fee per label) and the charges it covers.
• A shipment-level file every cycle, with each surcharge per parcel (The supporting detail files you should always request).
• On cost-plus, the carrier cost behind each label on request, by tracking number.
• A dispute window that starts when complete detail arrives (a negotiated change; otherwise it usually runs from the invoice).

We found no public figure for markup size with a stated method. To negotiate the number or the basis, see Negotiating shipping markup and carrier discounts.