When a card advertises bonus rewards at grocery stores, most people assume any place that sells food counts. It does not. Whether you earn a grocery multiplier at Walmart or Costco has almost nothing to do with the bread and milk in your cart and almost everything to do with a four-digit code attached to the store. Understanding that code explains why warehouse and big-box rewards feel so unpredictable.
Nothing here is financial advice. Reward category rules vary by issuer and change over time, so always confirm the current terms on your card's official page before you act.
What a merchant category code is
A merchant category code (MCC) is a four-digit number that describes what a business primarily sells. The card networks define the master list. Visa publishes its codes in the Visa Merchant Data Standards Manual, and Mastercard publishes its list in the Quick Reference Booklet, Merchant Edition. American Express maintains its own equivalent. When a merchant signs up to accept cards, its payment processor assigns it an MCC based on the network's definitions.
For groceries, the relevant codes are simple to name. Grocery stores and supermarkets are MCC 5411. Wholesale clubs are MCC 5300. Discount stores and department stores sit under their own codes again. These categories are not interchangeable, and your card treats them very differently.
See the glossary for short definitions of MCC and other terms used here.
How your card decides whether to pay a bonus
Here is the part that surprises people. Your card does not look at your receipt. It looks at the merchant's code.
As NerdWallet Canada puts it, codes and the bonus rewards tied to them are assigned at the macro level, meaning the overall retailer, rather than the micro level of what you actually buy. Ratehub makes the same point: a big-box retailer that sells groceries may still be treated as a discount store, department store, or warehouse club rather than a grocery store for rewards purposes. In short, it is about where you shop, not what you buy.
So when a card promises bonus points or cash back on groceries, what it really means is bonus rewards on purchases at merchants coded as grocery stores (MCC 5411). Buy a cart of food somewhere coded as a wholesale club or a discount store, and the grocery multiplier simply does not fire. You earn the card's base rate instead.
Why Costco is coded as a warehouse club
Costco is the cleanest example. It is a membership warehouse club, and it is generally coded as MCC 5300, wholesale clubs, not as a grocery store. That single code is why food bought at Costco usually earns only your card's base rewards, even though most of a typical Costco run is groceries.
This catches a lot of Canadians out, because Costco is where many households do their biggest food shop. If grocery rewards matter to you, the warehouse coding means a strong flat-rate card can easily beat a grocery-bonus card at Costco. Costco Canada also has its own accepted-network rules at checkout, which narrows your card options further. We break down the best fit in our guide to the best cards for Costco.
Why Walmart is even weirder
Walmart is messier than Costco because its coding is not consistent. A standard Walmart discount store is often coded as a discount or department store rather than a grocery store, so it may not trigger a grocery bonus at all. NerdWallet Canada notes from direct experience that Walmart discount stores are not categorized as a grocery store by Visa, and that a statement showed no bonus rewards earned there.
It gets more tangled because the answer can change with the network, the issuer, and even the specific location. A purchase may be treated as grocery by one issuer and not another, and a full-line Walmart Supercentre that sells fresh food can code differently from a smaller discount-format store. There is no single rule that holds across every card and every store. Our guide to the best cards for Walmart walks through how to play this in practice.
Wholesale clubs versus grocery stores
It helps to see why the networks draw the line where they do. A grocery store (MCC 5411) is defined around selling food and household staples as its primary business. A wholesale club (MCC 5300) is built on a membership model selling a broad mix of goods in bulk, from food to tires to electronics, often at warehouse scale. From the network's point of view those are different kinds of business, so they get different codes, and your rewards follow the code rather than your intent.
The same logic explains other oddities. A pharmacy that sells groceries may code as a drug store. A gas bar attached to a grocery banner often codes as a fuel merchant. A retailer that runs several formats can carry several codes. This is why two trips that feel identical can earn different rewards.
How to check what a card will actually earn
You cannot rely on the store's name or on your own sense of what it sells. You also will not find the MCC printed on your statement, and the networks do not publish per-store codes. The reliable approach is to test it.
- Make one small purchase at the store with the card you are considering.
- Wait for it to post, then check your rewards activity or statement to see how it was categorized and whether a bonus rate applied.
- Only then commit your larger or recurring spending there.
You can also call your issuer, which can sometimes confirm how a specific merchant is coded, and you should always read the bonus-category fine print in your card's reward terms, since many issuers explicitly state that warehouse and discount stores are excluded from grocery bonuses.
If grocery earning is your priority, choosing a card whose bonus reliably triggers at the stores you actually use matters more than the headline multiplier. Our roundup of the best cards for groceries in Canada ranks options with that real-world coding in mind. For households that do most of their food shopping at a warehouse club, a high flat-rate card often wins, because no grocery code means no grocery bonus no matter which card you carry.
The bottom line
Merchant category codes, not your receipt, decide whether a grocery bonus pays out. Costco is typically a wholesale club, standard Walmart is often a discount or department store, and both can quietly miss the grocery multiplier you were counting on. Codes are assigned per merchant and can vary by network, issuer, and location, so test a small purchase, read your card's reward terms, and pick the card that earns where you actually shop. Confirm the current rules with your issuer before making a decision.
Frequently asked
What is a merchant category code (MCC)?
An MCC is a four-digit code that the card networks (Visa, Mastercard, American Express) and the merchant's payment processor assign to a business to describe what it primarily sells. Grocery stores and supermarkets use MCC 5411, while wholesale clubs use MCC 5300. Your card looks at this code, not your receipt, to decide whether a bonus category applies.
Why do Costco purchases not earn my grocery bonus?
Costco is generally coded as a wholesale club (MCC 5300), not a grocery store (MCC 5411). Because rewards are triggered by the store's code rather than the items in your cart, food bought at Costco usually earns the card's base rate instead of any grocery multiplier. Always confirm in your card's reward terms.
Does Walmart count as a grocery store for rewards?
It depends on the network, the issuer, and the specific location. Standard Walmart discount stores are often coded as discount or department stores rather than grocery, so they may not trigger a grocery bonus, while some Walmart Supercentres can code differently. Test a small purchase and check how it posts.
How can I find out what MCC a store uses?
Networks do not publish per-store codes and you will not see the MCC on your statement. The practical method is to make a small purchase, then check your rewards activity or statement to see how it was categorized before spending more there. Your issuer can sometimes confirm by phone.
Can a store have more than one merchant category code?
Yes. A large retailer can operate different locations, banners, or checkout systems under different codes, and gas bars or pharmacies inside a big-box store may code separately. That is why two visits to what feels like the same chain can earn different rewards.
Sources
Every figure in this guide traces to a primary source. Confirm details on the official page before you apply. Nothing here is financial advice.