What happens to email and SMS consent when you merge customers

A merge joins two records into one, and each record carries a subscription choice. This page follows that choice through a Shopify merge and a Klaviyo merge, and says where the pages of Shopify and Klaviyo stop. It describes how the two systems behave. It is not legal advice, and the last section says who to ask.

Shopify’s rule

Shopify’s Help Center, in the section on limitations for merging customer profiles, says: “If the customer is subscribed to email and SMS text marketing in one profile, but not in the other, then the merged profile is subscribed.”

Two other lines from the same page matter here. “After the profiles are merged, you can’t reverse the process”, and “The customer isn’t notified when you merge their customer profiles.” The shopper learns nothing, and you can’t take the merge back.

What Klaviyo does when both profiles hold the same status

Klaviyo’s help page on merging says: “Merging profiles is permanent and cannot be undone.” It adds: “Email consent and suppression information is merged along with the profiles.” Its help page on how Klaviyo works out which profiles are the same person describes how the records combine:

• When only the source profile has an email consent record, “Klaviyo uses that record on the destination profile.”
• When both profiles have the same status, “Klaviyo keeps the earlier consent date.”
• When only the source profile has an email suppression record, “Klaviyo copies that record to the destination profile.” With the same reason on both, “Klaviyo keeps the earlier suppression date.”

The page describes these cases for profiles that share an email address. It does not describe what happens when the two profiles hold different statuses, and it does not say that the newer choice wins. We found no Klaviyo statement for that case (we read the page on October 26, 2026), so we make none. After any merge, open the profile you kept in Klaviyo and read its consent and suppression status.

What a Klaviyo merge never does

Klaviyo’s page states that a merge “does not collect new consent”. It also does not mean the customer can receive messages on every channel, and “Consent is never added to a phone number without explicit consent from that specific phone number.”

SMS follows the phone number. Klaviyo’s SMS page says “SMS consent is tied to the phone number”. A profile that holds an email address and a phone number has not agreed to both channels because of that. Profiles made by a phone-only signup can stay apart from an email-only profile when Klaviyo can’t link them.

Coupons and flows after a Klaviyo merge

Two practical effects come from the same Klaviyo page.

• Coupons: “Active coupons assigned to the source profile are not reassigned to the destination profile.” A code sent to the merged-away profile stops belonging to the person you kept.
• Flows: for flows triggered by a list or segment, when both profiles are still active, “the source profile’s flow is canceled, and the destination profile continues uninterrupted.”

Why a wrong merge matters

Shopify’s rule runs in one direction: a subscribed profile makes the merged customer subscribed. If two different people end up merged, the subscription of one profile applies to the merged customer. The other person could then be mailed without having agreed.

That is why every MergeGuard merge starts with evidence and your decision, either your confirmation or automatic merging you switched on for strong matches or groups that need your judgment. Keep relatives, flatmates and close calls separate. See sending the same newsletter twice for how to deal with duplicate addresses without a merge.

What MergeGuard does

MergeGuard for Shopify follows Shopify’s rule, because it merges through Shopify. It never changes consent itself, and it sends no messages. A list sync to Klaviyo never changes consent either.

Merging profiles in Klaviyo is a separate, optional step that MergeGuard leaves off until you turn it on. Klaviyo’s own rules then decide the merged profile’s consent and suppression, and a Klaviyo merge can’t be undone. Help explains how to merge repeat profiles in Klaviyo and what happens when you merge customers.

What the regulator says about valid consent

The UK Information Commissioner’s Office, a regulator, sets out what valid consent under UK GDPR looks like. Its page says: “Silence, pre-ticked boxes or inactivity should not therefore constitute consent.” It says consent “should be unbundled from other terms and conditions”, lists “the right to withdraw consent easily and at any time” among the conditions, and says you “must be able to demonstrate that someone has consented.”

Those lines come from one regulator’s guidance, and rules differ between the US, the UK and the EU. A subscription carried over by a merge is a recorded status. Whether that status meets the rules where your customer lives is a legal question.

Shopify’s Help Center tells merchants to “consult with a local lawyer who is familiar with data protection laws” for questions about which laws apply to them. Do that before you rely on a merged subscription for a campaign.