Duty is charged on value, and for goods invoiced in a foreign currency that value moves with the exchange rate between order and entry. A contract silent on currency silently assigns all of that movement, and its duty consequences, to one side. Currency clauses exist to share that risk deliberately, and on tariff exposed goods they matter twice, because the rate swing is taxed as well as paid.
How currency movement becomes a duty cost
Customs converts the invoice value at the rate in force around entry, so a currency that strengthens between purchase order and arrival raises both the amount you owe the supplier in your own currency terms and the dutiable value the tariff percentage applies to. The tariff multiplies the exchange movement: on a high duty line, a five percent currency swing can cost noticeably more than five percent by the time duty is counted.
The reverse also happens, and fairness cuts both ways. A weakening supplier currency lowers your duty and your cost, and a supplier who accepted all downside in the contract will, reasonably, come looking for the upside to be shared too. Clauses negotiated as genuine two way sharing survive those conversations. Clauses written as one way protection tend to be renegotiated at the worst moment, mid swing, with a shipment on the water.
The common clause shapes
A band clause leaves prices fixed while the rate stays inside an agreed range, and triggers a price adjustment, often shared by formula, outside it. A index clause ties the price to a published rate at a defined date, order, shipment, or entry, removing argument about which rate applies. A currency of invoice change, splitting orders between two currencies, diversifies the exposure instead of contracting around it, and suits suppliers with costs in more than one currency.
Whichever shape you choose, define the mechanics in the clause itself: the rate source, the date, the adjustment formula, and how duty effects are treated in the sharing. Vague clauses that promise to negotiate in good faith when rates move are diaries of future disputes. The time to agree the arithmetic is when neither side knows which way the rate will go, because that ignorance is what makes agreement fair and therefore possible.
Interplay with tariff change clauses
Many contracts now carry both a currency clause and a tariff change clause, and the two must be drafted to meet without double counting. If the tariff clause passes duty changes to one party and the currency clause reprices the goods, a currency driven duty increase can be charged twice through both mechanisms. Read them together, define which clause owns duty effects arising from value changes, and state it in one sentence both sides can find.
Review the pair whenever either risk regime shifts: a new tariff action, a currency that leaves its historical band, a change of sourcing country. Contracts in international trade are not set and forget documents anymore; they are risk allocation systems that need the same periodic review as the costs they govern. A yearly contract review keyed to your tariff and currency exposure list is a small meeting with an outsized return.
Negotiating the clause without poisoning the relationship
Open with the shared interest: both sides want predictable margins and a contract that does not need emergency renegotiation every time a rate moves. Suppliers fear open ended exposure to a currency they do not control, exactly as you do, so a banded, formula based sharing is usually an easier yes than a demand that one side absorb everything. Offer symmetry explicitly, and put a worked example with real numbers in the draft; arithmetic persuades where principles argue.
Start the clause on new orders rather than attempting to retrofit it onto goods already priced and shipped. Retrofitting reads as moving a loss, while forward application reads as planning, and the same clause will be received entirely differently depending on which it is. The relationship is an asset on your balance sheet in everything but name; spend it on the contracts that govern the future.
Keep reading
Related guides on this site: Foreign Trade Zones in a Tariff Spike: Timing Duty Instead of Avoiding It Mapping Tariff Exposure Across Supplier Tiers: Beyond Your Direct Imports Answers for teams shipping Shopify orders across borders.
Frequently asked questions
Why do currency swings change my tariff bill?
Duty is charged as a percentage of the customs value, which is converted from the invoice currency at the rate around the time of entry. If that currency strengthens before entry, the dutiable value rises and so does the duty, on top of the higher cost of the goods themselves.
What is a band clause in a supplier contract?
A clause that keeps prices fixed while the exchange rate stays within an agreed range, and adjusts prices by a stated formula, usually sharing the movement, when the rate moves outside the band. It protects both sides from extreme swings while leaving ordinary movement alone.
Can currency and tariff clauses conflict?
Yes. If a tariff clause passes duty changes on and a currency clause reprices the goods, a currency driven rise in duty can be charged through both. The clauses should be read together and state clearly which one covers duty changes caused by value movements.
Should currency risk clauses be one way or shared?
Shared and symmetric clauses last longer. A clause that only protects one side gets renegotiated under pressure when the rate moves the other way, usually at the worst time. Two way sharing by formula, agreed before anyone knows the direction, is the version both sides honour.