Supply agreements have always had to answer one question: when input costs move, who absorbs it. For long periods that question was largely theoretical for many categories, and the standard answer of fixed price for the term worked well enough. Recent years have made it concrete again, through commodity volatility, freight dislocation, energy prices, currency movement and changes to duties and tariffs.
The contractual response has been widespread adoption of pass-through, index-linked and surcharge mechanisms. What has not followed is discipline about how those mechanisms are built and operated. A clause that adjusts price by reference to an index is only as good as the correlation between that index and the cost actually incurred, and only as useful as the party that remembers to invoke it inside the notice period.
This article covers the design decisions that determine whether a pass-through clause functions, the failure modes that appear when it does not, and what has to be tracked after signature for the mechanism to be worth having. The framing applies equally to a buyer trying to resist an unjustified increase and to a supplier trying to recover a real one.
The four decisions that determine whether it works
These are design choices made at negotiation, and each one has a predictable failure mode when it is left loose.
- Index selection and basis, the specific published reference, including grade, region, currency and delivery basis, chosen because it correlates with the cost incurred rather than because it is well known.
- Trigger threshold and measurement period, the movement required before an adjustment applies and the averaging window used, which together prevent both trivial adjustments and opportunistic timing.
- Notice window and adjustment cadence, when a claim must be made after the trigger is met, and how often price can change, which determines whether the mechanism is usable operationally.
- Evidence and audit rights, the documentation required to support a claim and the right to verify it, without which every adjustment becomes a negotiation.
- Symmetry and floors, whether the mechanism operates in both directions and whether floors or caps apply, because a one-way clause is a price increase with a schedule.
Index correlation is where most of the value is won or lost. A converter buying a specific resin grade delivered to a specific region is exposed to a price that may diverge materially from the headline index for that polymer family. The gap between the index and the incurred cost is basis risk, and it sits with whoever agreed the index without checking the correlation.
Commodity indices do not reflect changes in duties, tariffs or trade measures. If those risks matter to the category, they need a separate, explicitly drafted trigger with its own evidence requirement, rather than being left to a force majeure or material adverse change argument after the fact.
How pass-through clauses fail
The failures are operational as often as they are contractual, and they are visible in advance if anyone is tracking the mechanism.
- Basis risk nobody quantified. The index moves differently from the incurred cost, so one party absorbs a persistent gap. Test the correlation against your own purchase history before agreeing the reference, not after the first adjustment cycle.
- Notice windows missed. A valid adjustment goes unclaimed because the window closed. This is the most common single failure, and it favors whichever party has better contract administration rather than the better commercial position.
- Adjustment on request. Without a stated threshold and measurement period, every movement becomes a negotiation, which consumes commercial time and produces inconsistent outcomes across similar suppliers.
- One-way mechanisms. Clauses that adjust upward on cost increases but contain no downward mechanism leave price elevated after input costs normalize, often for the remainder of a multi-year term.
- No propagation to downstream contracts. A manufacturer accepts pass-through on the inbound side without a matching mechanism in its customer agreements, absorbing the whole movement in margin.
A five-step way to operate the mechanism
Step 1, Test index correlation before agreeing it
Compare candidate indices against your own historical purchase prices for the specific grade and region. Choose the reference with the best correlation, and record the basis risk you are accepting on the ones that remain.
Step 2, Write the mechanism as parameters
Extract index, basis, threshold, measurement period, notice window, cadence, floors and caps as structured fields on the contract record rather than leaving them in prose that has to be re-read each cycle. This is the same structuring step described in the supplier contract automation guide.
Step 3, Track the notice window as an obligation
Create a dated obligation triggered by the measurement period close, owned by the party that benefits, with enough lead time to prepare the evidence. Missed windows stop being the default outcome.
Step 4, Reconcile adjustments against the mechanism
Check each applied adjustment against the modeled parameters rather than accepting the counterparty calculation. Small arithmetic differences compound quietly across a multi-year term.
Step 5, Map inbound and outbound exposure together
Compare pass-through terms in supplier agreements against the equivalent terms in customer agreements to find categories where the organization is absorbing the movement on both sides.
Hold pricing mechanics as data, not prose
Aavenir keeps index parameters, thresholds and notice windows on the contract record, with adjustment windows tracked as dated obligations.
Why the inbound and outbound view has to be joined
Most organizations analyze pass-through exposure one contract at a time, usually when a specific supplier requests an increase. That framing hides the position that matters. A manufacturer with index-linked terms on the supply side and fixed pricing on the customer side has quietly written an option against itself, and the size of that option only becomes visible when both sides are viewed as a portfolio. The analysis is straightforward once the pricing mechanics exist as structured fields rather than as clauses: group agreements by input category, compare the aggregate inbound adjustment exposure with the outbound mechanisms that could recover it, and rank the gaps by annual value. That exercise routinely identifies categories where a modest change at the next renewal removes a large share of the exposure, and it also identifies the opposite case, where an organization holds recovery mechanisms it has never invoked because nobody connected the inbound movement to the outbound entitlement. The wider set of post-signature terms that leak value when untracked is covered in stopping value leakage.
Mechanism types and where each fits
The table compares the common structures. Most portfolios use several, and the choice should follow the volatility and the measurability of the underlying cost rather than category convention.
| Mechanism | How it works | Fits when | Main risk |
|---|---|---|---|
| Fixed price for term | No adjustment during the term | Short terms, stable inputs | Full exposure to a shock |
| Index-linked adjustment | Price moves with a published reference | Liquid, well-indexed commodities | Basis risk against incurred cost |
| Surcharge | Separate line added above base price | Volatile discrete inputs such as freight or energy | Surcharge persists after cost normalizes |
| Open book with agreed margin | Verified cost plus fixed margin | Strategic, high-spend relationships | Administration and audit burden |
| Tariff and duty trigger | Adjustment on a defined trade measure change | Cross-border sourcing exposure | Ambiguous evidence and attribution |
A pass-through clause is a mechanism, and mechanisms have parameters and dates. Written as prose and filed, the clause allocates risk to whoever administers contracts more attentively. Written as structured parameters with tracked notice windows, it does what it was negotiated to do. The difference is rarely legal sophistication; it is whether the numbers and the dates live somewhere that raises work. Organizations that make that change usually find the first year pays for itself on claims that would otherwise have lapsed, before any of the portfolio-level repricing benefits arrive.
For related guidance, see Cost pass-through clauses, a practical control plan, Price adjustment clauses in direct material contracts and Tariff and trade clause control for manufacturers.
