Cross-border dairy trade has moved from a technical quota dispute to a direct cost at the border. Since September 8, Canada has imposed a 25% surtax on U.S. cheese and a 50% surtax on covered whey and natural milk-constituent products as part of its retaliation against U.S. trade measures. Applying those rates to 2025 trade values produces potential monthly duty exposure of about US$6.21 million on cheese and whey alone.
That figure is best read as a benchmark, not a customs receipt. It assumes last year’s trade continues at roughly the same pace and does not subtract tariff relief, drawback claims, rerouted shipments, lower volumes, or changes in prices. Even with those caveats, it puts a concrete number on how quickly the dairy dispute can affect processors, exporters, importers and ultimately farm-level economics on both sides of the border.
How the US$6.21 Million Estimate Is Calculated
The US$6.21 million figure comes from a relatively simple calculation built on 2025 customs values. University of Wisconsin–Madison Extension reports that U.S. cheese exports to Canada were worth about US$134 million in 2025. Dividing that by 12 gives roughly US$11.17 million a month. A 25% Canadian surtax on that monthly trade produces about US$2.79 million in potential duties.
For whey and products consisting of natural milk constituents under HS heading 0404, the same analysis puts 2025 U.S. exports to Canada at about US$82 million, or roughly US$6.83 million a month. Applying Canada’s 50% surtax yields about US$3.42 million in monthly duty exposure. Add the two categories together and the result is about US$6.21 million. The important words are “up to.” The calculation assumes the same trade pattern continues after the tariffs, while actual importers can reduce orders, switch suppliers, seek relief, or absorb only part of the cost. The estimate therefore measures exposure at 2025 volumes rather than a guaranteed monthly tax collection.
Cheese Faces 25%, While Covered Whey Faces 50%
Canada’s measure is broader than a single tariff on one popular cheese. The federal counter-tariff list applies a 25% surtax across numerous cheese and curd classifications, including fresh, grated, processed, blue-veined, cheddar, mozzarella, Parmesan, Havarti, Swiss and other categories. Covered whey and modified whey products, including whey protein concentrate and powdered whey, face a 50% surtax. The same retaliatory package also reaches several other dairy ingredients, although the US$6.21 million headline isolates cheese and whey.
For importers, the mechanics are straightforward but expensive. Canada Border Services Agency calculates the surtax on the customs “value for duty,” and the charge is added on top of other applicable duties and taxes. A U.S.-origin cheese shipment with a value for duty of US$100,000 would therefore face a US$25,000 Canadian surtax if fully exposed. A comparable covered whey shipment would face US$50,000. Those examples help explain why buyers may alter purchasing decisions quickly: the tariff changes the landed cost before freight, warehousing, retail margins and downstream processing costs are considered.
The Dispute Began With Washington’s Dairy Action
The dairy retaliation did not begin in isolation. On July 20, President Donald Trump invoked Section 338 of the Tariff Act of 1930 to announce additional 50% duties on certain Canadian dairy products, arguing that Canada’s administration of dairy tariff-rate quotas discriminated against U.S. commerce. The duties were originally scheduled for August 19, then delayed for three days and ultimately took effect on August 22. Ottawa answered with a much wider package of countermeasures effective September 8, including the dairy surtaxes.
The legal and political history is more complicated than either side’s public messaging suggests. Washington has long objected to how Canada allocates access under its dairy tariff-rate quotas, especially for cheese. Yet the most recent USMCA dispute panel on those allocation rules, released in November 2023, found by a two-to-one majority that the Canadian measures challenged by the United States were not inconsistent with the agreement provisions cited by Washington. That does not erase U.S. complaints, but it matters for context: the current tariff fight reflects an unresolved policy dispute, not a simple finding that one side definitively violated the trade pact.
Canada Remains a Major Market for American Dairy
Canada is important to U.S. dairy exporters even though the new tariffs do not cover every dairy product moving north. U.S. dairy sales to Canada were about US$1.3 billion in 2025, making Canada the second-largest foreign market after Mexico and accounting for roughly 14% of U.S. dairy exports in the University of Wisconsin–Madison analysis. Cheese and whey together represented about US$216 million of that trade based on the same customs data.
The targeted nature of the retaliation is equally important. Butter and milk fats were worth about US$228 million in U.S. exports to Canada in 2025 and were not included in the dairy retaliation described by the Wisconsin analysis. Fluid milk and cream, yogurt and ice cream also were outside the core cheese-and-whey measures. That means the dispute does not shut down U.S. dairy trade with Canada; instead, it changes the economics of specific product streams. For a processor whose Canadian business is concentrated in cheese or whey ingredients, however, that distinction offers little comfort. Exposure depends less on the total size of U.S. dairy exports than on which products a company actually sells across the border.
Relief Programs Mean the Maximum May Not Be Collected
The maximum-duty calculation also overstates what some companies may ultimately pay because Canada has several relief mechanisms. CBSA says its Duties Relief and Duty Drawback programs are available for surtax paid or payable under the 2026 order, subject to the relevant rules. Finance Canada also maintains a remission framework for cases where tariffed inputs cannot reasonably be sourced domestically or from non-U.S. suppliers, or where exceptional circumstances could cause serious economic harm.
The practical distinction is especially important for dairy ingredients used in manufacturing. Canadian guidance allows certain tariff relief for goods that are re-exported, while U.S. dairy industry groups have said shipments moving through Canada’s Import for Re-Export Program and eligible manufacturing or processing uses can qualify for relief. By contrast, U.S. dairy sold directly into the Canadian retail market can still face the full retaliatory tariff. This is why the US$6.21 million figure should not be interpreted as money Ottawa will necessarily collect every month. It is the gross exposure if 2025 trade continues and no qualifying relief is used, not a net estimate after customs programs and commercial adaptation.
The Effects Can Reach American Farm Milk Prices
The larger economic question is not only who pays the duty at the border, but what happens when exporters lose part of a market. A U.S. supplier can absorb some of the tariff, raise its Canadian price, redirect product to another country or sell more into the domestic market. Each response shifts the burden differently. University of Wisconsin–Madison’s work emphasizes that cheese and whey matter because both feed directly into the U.S. Class III milk-pricing system used across much of the dairy economy.
Under USDA pricing formulas, cheese and dry-whey values are inputs into Class III prices. The Wisconsin analysis estimates that a one-cent-per-pound decline in cheese prices would reduce Class III by about 10 cents per hundredweight, while a one-cent decline in dry whey would reduce it by roughly six cents. Its scaled scenario for a sustained Canada-only action produces an anchor range of about 20 to 35 cents per hundredweight, within a broader planning range of 10 to 50 cents. Those numbers are scenarios, not forecasts, but they show how a border measure affecting a relatively small share of total milk output can still spread through farm milk checks.
Washington Has Gone Beyond Tariffs on Canadian Whey
The trade fight became even more complicated when Washington moved from tariffs to an outright import restriction on part of Canada’s dairy trade. Effective September 29, U.S. Customs and Border Protection began rejecting covered Canadian dairy entries identified under President Trump’s Proclamation 11062, including specified whey products. Goods imported before the cutoff but not yet entered for consumption remained subject to the earlier 50% duty, while newly covered shipments after the effective date could not simply pay a higher tariff and enter.
That matters because the Canadian and U.S. measures can push U.S. whey prices in opposite directions. Canada’s 50% surtax can reduce demand for American whey and leave more product in the U.S. market, which would normally weigh on prices. The U.S. restriction on Canadian whey can simultaneously remove imported supply from the American market, which can support prices. University of Wisconsin–Madison specifically cautions that the net direction is not determined by the available evidence. In other words, a simple claim that retaliation must lower U.S. dairy prices—or raise them—misses the two-way nature of the current border restrictions.
The US$6.21 Million Figure Is a Benchmark to Watch
For now, the US$6.21 million monthly figure is most useful as a stress test. Canada’s current official counter-tariff list continues to show the September 8 measures, while the commercial response is still developing. Importers can seek relief, processors can adjust sourcing, and U.S. exporters can redirect sales. Any of those moves would reduce the amount of trade actually exposed to the headline duty calculation. The real impact will become clearer only as post-tariff customs data accumulate and companies reveal how much business was rerouted or lost.
The political outlook is just as unsettled. Canada’s chief trade negotiator said this week that officials remain in contact with their U.S. counterparts but that there was no clear timetable for a return to detailed formal negotiations. President Trump, meanwhile, said on October 23 that Canada was working hard to reach a deal. Those signals leave room for negotiations without guaranteeing relief for dairy. Until the rules change, cheese and whey exporters face a new cost structure, Canadian buyers face stronger incentives to find alternatives, and the US$6.21 million estimate remains a practical measure of what one month of unchanged trade could cost before exemptions and adjustments.
