UK email law allows soft opt-in for existing customers — most Shopify stores are over-restricting their list and leaving revenue uncollected

Soft opt-in is a PECR provision that allows businesses to send commercial email to existing customers about similar or related products without requiring a new consent action. It applies when the customer's contact details were collected during a prior transaction, the message relates to similar goods or services, and the customer was given a clear opportunity to opt out at collection and in every subsequent message. Double opt-in is a deliverability best practice that requires a subscriber to confirm their email address by clicking a link in a confirmation email after signing up. Double opt-in is not required by UK PECR or UK GDPR for existing customers contactable under soft opt-in — applying it to that audience reduces list size without adding legal protection.

Klaviyo's email templates support Liquid templating, which allows you to reference order value data pulled from the Shopify integration. The standard approach is to retrieve the cart value from the event properties, divide by three, and display the result formatted as a GBP amount with the label "3 payments of." Klarna's own marketing materials recommend displaying the instalment amount wherever the full price is shown. The display in the abandoned cart email is most effective when placed immediately below or beside the total order value, not in the footer. Klaviyo's Klarna block is available for accounts with Klarna configured in Shopify, but the manual Liquid approach gives more layout control.

Review requests should be sent after delivery confirmation, not after order placement. UK standard delivery takes 2-5 working days, and express delivery takes 1-2 working days. Sending a review request before the product arrives produces near-zero response rates and increases the probability that any response reflects frustration about delivery timing rather than product quality. The trigger should be the delivery confirmation event, not the order created event. Delivery confirmation data can be passed to Klaviyo through Royal Mail tracking integration, AfterShip, Parcel Panel, or similar apps that emit a webhook when a shipment is marked delivered. The review request email should arrive 24-48 hours after delivery confirmation.

SMS marketing is highly effective for UK e-commerce because UK consumers have very high SMS open rates — consistently measured at 95-98% across commercial sends. Klaviyo supports SMS natively in the UK through its built-in SMS product, which handles sender registration, compliance headers, opt-in collection, and flow integration. To set up UK SMS in Klaviyo, you register a UK sender number (long code or short code), configure an SMS-specific opt-in form or checkout consent checkbox, and build SMS steps into your existing flows. PECR requires explicit prior consent for SMS — soft opt-in does not cover text messages. The opt-in mechanism must clearly identify SMS as the channel being consented to.

When importing existing contacts to Klaviyo, each contact record must have a verifiable consent record — the date consent was obtained, the channel through which it was obtained, and the consent method used (for example, checkout opt-in checkbox, sign-up form, or PECR soft opt-in). This information should be stored as custom profile properties in Klaviyo, not just held in a separate spreadsheet. Contacts without a verifiable consent record should not be imported for marketing purposes. Lists purchased from third parties or scraped from websites cannot be imported for commercial email under UK GDPR or PECR. After import, the suppression list must be checked to ensure previously unsubscribed contacts are not re-added.