How Shopify identifies a customer for a discount

A discount code asks one question at checkout: has this customer used it before? Shopify answers by looking at contact details, and a shopper can change those between orders. This guide explains what the answer is based on, who a code can reach, why a new email can get past a limit, and how to run offers so the gaps matter less. It follows Shopify’s Help Center, and where we reason beyond it, the text says so.

What the limit checks

On a percentage or fixed-amount discount, Shopify’s Help Center describes the option Limit to one per customer as a way “to limit the discount to one use per customer by tracking a customer’s email address or phone number.” That page describes no check of names, addresses or cards.

A note on the mobile admin: the same page says of this limit, “This only applies to fixed value discounts.” If you set discounts from your phone, read that page before you rely on the limit.

Shopify’s Help Center says “Each profile can have only one email address” (Managing customers). A shopper with a second email is a second profile, and the limit has no reason to link the two.

Who can be eligible

Before a code is limited, you choose who can use it. Shopify’s discount settings offer four choices:

Segments and specific customers work through the same contact details. The Managing discount codes page says those customers “can be identified when they check out using a valid email address or phone number.” Shopify’s page does not say what happens when a shopper checks out with other details, so test it on your own store.

Why a new email can beat the limit

This section is our reasoning from the two sentences above, and the Shopify Community discusses the same gap (a merchant thread on welcome-discount reuse).

The limit tracks an email address or a phone number. So a shopper with a new email and a new phone looks like a new customer to it. Shopify’s page does not say whether a match on one detail is enough when the other has changed. Treat the limit as a guard against casual reuse, and expect that it can be passed by someone with a second address.

Most second addresses have an ordinary cause. People change email, mistype one, forget an account, or check out through a wallet that fills in a different address. The merchant-reported causes are listed in why Shopify creates duplicate customers.

Signals worth a review, and what they do not prove

A few details are worth a look when two profiles used the same welcome code: the same phone number, emails that differ by one character or a number, and the same address with the same name. Welcome discount reuse ranks these and explains each one.

We found no study that measures how often discount codes are reused through extra accounts, so we won’t give a rate. Shared details can also point to two people:

• Partners, flatmates, parents and children share an address.
• Gift buyers send orders to someone else’s address.
• Offices share a phone number.

A match is a reason to look, and it says nothing about intent. In MergeGuard you can mark relatives as family members so they stay out of a duplicate review.

Design the offer so the limit matters less

Changes to the offer reach every customer at once, so they are fairer than chasing individual shoppers:

• Send a single-use code to the email that signed up, instead of showing one public code.
• Define “new customer” for yourself. The partner of an existing customer may be a new customer you want.
• Test before you rely on a setting. Place a test order with a second email and see what your discount does.

Duplicates and your discount reports

Any report that counts by profile treats a second profile as a second customer. A returning shopper on a new profile looks new in a count of new customers, and a regular who stopped using one profile looks like someone who left. Counting people puts a shopper’s orders and codes together. That is also why a win-back discount should go only to people who really stopped buying. Duplicates and repeat purchase rate shows the same distortion in another number.

If a group is clearly one person, merging the profiles puts their orders on one customer. A Shopify merge is permanent, and relatives or close calls should stay separate. MergeGuard never merges without your confirmation, unless you switch on automatic merging for strong matches or groups that need your judgment.