Tariff

What a tariff is on a service vendor invoice, how it differs from a rate card, and why unreviewed tariff terms create margin drift. Read the full guide.

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Tariff

A tariff is a vendor's published schedule of rates, rules and accessorial charges that governs what it can bill outside a negotiated contract. Margin drift is the gap between what a vendor contract says and what the invoice actually charges. Tariffs matter because they often fill in the terms a contract leaves silent, and an AP team that never reads the tariff has no way to check whether a charge was even allowed.

Executive Summary

A tariff is the default rulebook a vendor applies when a contract does not override it. Freight carriers, utilities and telecom providers all publish tariffs that define accessorial fees, minimum charges and adjustment mechanics. When a contract references a tariff, the tariff terms become enforceable even though they never appear on the invoice itself.

The mechanism that creates drift is silence. A negotiated rate card sets the headline price, but the tariff still governs everything the rate card does not mention. A vendor can raise a tariff-based fee without renegotiating the contract, and the invoice will look ordinary because the fee is technically authorized.

Reviewing invoices against the contract alone misses this. Reviewing them against the tariff the contract incorporates closes the gap.

1. What does a tariff actually govern?

A tariff governs the charges and conditions a contract does not spell out itself: accessorial fees, minimum shipment charges, fuel surcharge formulas, and the rules for adjusting rates over time. It is published by the vendor, not negotiated line by line, and a contract typically incorporates it by reference rather than restating its terms in full.

A shipping contract might set the base linehaul rate and leave every accessorial charge to the carrier's published tariff. A utility contract might set volume pricing and leave demand charges and late fees to a filed tariff. The contract and the tariff work together, and reviewing only one leaves the other unchecked.

2. How is a tariff different from a rate card?

A rate card lists the specific prices negotiated for one customer's committed volume. A tariff is the vendor's general published schedule that applies broadly unless a rate card overrides it. Where the rate card is silent, the tariff fills the gap, so an invoice can be correct against the rate card and still be wrong against the tariff terms it also has to satisfy.

Confusing the two is common because both arrive as tables of numbers. The distinction that matters for audit purposes is scope: a rate card overrides the tariff only where it explicitly says so, everywhere else the tariff still applies in full.

3. Why does an unreviewed tariff create margin drift?

Margin drift appears when a tariff-based charge changes and nobody on the buyer's side notices, because the change is technically valid under the incorporated tariff and never shows up as a contract violation. The invoice cites a tariff schedule that may have been updated since the contract was signed, and three-way matching against a purchase order does not test that schedule at all.

Three-way matching checks the invoice against the purchase order and receipt. It does not test whether a cited tariff rate matches the version the contract actually incorporated by date or edition. That gap is exactly where tariff-driven drift accumulates, quietly and without triggering any standard AP control.

4. Which categories rely most heavily on tariffs?

Freight, utilities and telecom are categories where tariffs carry significant weight in a service contract, because each of these vendors publishes rate schedules that regulatory or industry practice requires them to maintain. Reviewing spend in these categories means pulling the referenced tariff, not just the contract, before judging whether a charge is valid.

Auditing these categories means treating the tariff as a live document, not an attachment filed away at signing.

  • Freight and 3PL: Carriers publish accessorial and fuel surcharge tariffs that a linehaul contract incorporates by reference.
  • Utilities and energy: Filed rate schedules set demand charges and time-of-use rates outside the negotiated supply agreement.
  • Telecom and connectivity: Regulatory and equipment surcharges often sit in a carrier's general tariff rather than the service order.

For the wider pattern this sits inside, start with the margin drift guide.

5. Frequently Asked Questions (People Also Ask)

Is a tariff the same as a contract?

No. A contract is negotiated between the two parties. A tariff is published by the vendor and applies broadly, and a contract usually incorporates it by reference for anything the contract itself does not cover.

Can a vendor change its tariff without notifying us?

Tariff update practices vary by vendor and industry, so check the incorporation language in your contract for any notice requirement. This is general information, not legal advice.

Does three-way matching catch tariff errors?

Three-way matching checks the invoice against the purchase order and receipt. It does not test whether a cited tariff rate matches the version the contract incorporated, so tariff-based errors pass through undetected.

What is the difference between a tariff and a rate card?

A rate card holds the specific negotiated prices for one customer. A tariff is the vendor's general published schedule that fills in everything the rate card leaves unstated.

Which vendor categories use tariffs most?

Freight, utilities and telecom vendors commonly reference published tariffs inside their service contracts for accessorial fees, demand charges and regulatory surcharges.

How do I check whether a billed tariff charge is valid?

Pull the tariff edition the contract actually incorporates, compare its terms to the billed charge, and confirm the edition date matches what the contract references rather than a newer or older version.

Does a fixed-scope diagnostic review tariff terms?

A contract compliance review checks invoice charges against contract terms including incorporated tariffs, as part of a broader review of vendor billing across service categories.

Is tariff drift the same as a price increase?

Not necessarily. A legitimate price increase is disclosed and agreed. A tariff-based charge can rise without direct notice to the buyer if the contract already incorporated the tariff's adjustment mechanism.

1. What does a tariff actually govern?

A tariff governs the charges and conditions a contract does not spell out itself: accessorial fees, minimum shipment charges, fuel surcharge formulas, and the rules for adjusting rates over time. It is published by the vendor, not negotiated line by line, and a contract typically incorporates it by reference rather than restating its terms in full. A shipping contract might set the base linehaul rate and leave every accessorial charge to the carrier's published tariff. A utility contract might set volume pricing and leave demand charges and late fees to a filed tariff. The contract and the tariff work together, and reviewing only one leaves the other unchecked.

2. How is a tariff different from a rate card?

A rate card lists the specific prices negotiated for one customer's committed volume. A tariff is the vendor's general published schedule that applies broadly unless a rate card overrides it. Where the rate card is silent, the tariff fills the gap, so an invoice can be correct against the rate card and still be wrong against the tariff terms it also has to satisfy. Confusing the two is common because both arrive as tables of numbers. The distinction that matters for audit purposes is scope: a rate card overrides the tariff only where it explicitly says so, everywhere else the tariff still applies in full.

3. Why does an unreviewed tariff create margin drift?

Margin drift appears when a tariff-based charge changes and nobody on the buyer's side notices, because the change is technically valid under the incorporated tariff and never shows up as a contract violation. The invoice cites a tariff schedule that may have been updated since the contract was signed, and three-way matching against a purchase order does not test that schedule at all. Three-way matching checks the invoice against the purchase order and receipt. It does not test whether a cited tariff rate matches the version the contract actually incorporated by date or edition. That gap is exactly where tariff-driven drift accumulates, quietly and without triggering any standard AP control.

4. Which categories rely most heavily on tariffs?

Freight, utilities and telecom are categories where tariffs carry significant weight in a service contract, because each of these vendors publishes rate schedules that regulatory or industry practice requires them to maintain. Reviewing spend in these categories means pulling the referenced tariff, not just the contract, before judging whether a charge is valid. Auditing these categories means treating the tariff as a live document, not an attachment filed away at signing. - [Freight and 3PL](/glossary/freight-and-3pl-audit): Carriers publish accessorial and fuel surcharge tariffs that a linehaul contract incorporates by reference. - [Utilities and energy](/glossary/utilities-and-energy-audit): Filed rate schedules set demand charges and time-of-use rates outside the negotiated supply agreement. - [Telecom and connectivity](/glossary/telecom-and-connectivity-audit): Regulatory and equipment surcharges often sit in a carrier's general tariff rather than the service order. For the wider pattern this sits inside, start with the [margin drift](/insights/margin-drift-spend-leakage-guide) guide.

Questions & Answers

Is a tariff the same as a contract?

No. A contract is negotiated between the two parties. A tariff is published by the vendor and applies broadly, and a contract usually incorporates it by reference for anything the contract itself does not cover.

Can a vendor change its tariff without notifying us?

Tariff update practices vary by vendor and industry, so check the incorporation language in your contract for any notice requirement. This is general information, not legal advice.

Does three-way matching catch tariff errors?

Three-way matching checks the invoice against the purchase order and receipt. It does not test whether a cited tariff rate matches the version the contract incorporated, so tariff-based errors pass through undetected.

What is the difference between a tariff and a rate card?

A rate card holds the specific negotiated prices for one customer. A tariff is the vendor's general published schedule that fills in everything the rate card leaves unstated.

Which vendor categories use tariffs most?

Freight, utilities and telecom vendors commonly reference published tariffs inside their service contracts for accessorial fees, demand charges and regulatory surcharges.

Margin Drift Resources