Why collect opt-in at checkout
Adding WhatsApp (or RCS/SMS) as a communication channel at checkout lets you stay in touch with your customers via a platform they use daily. This increases your chances of conversion and retention, while enriching your contact base opted in on these channels.
This collection lever works exactly the same way for WhatsApp and for RCS/SMS: it's not a channel reserved for WhatsApp only.
How to integrate collection into checkout
If you already collect SMS opt-ins:
Simply update the text of the existing checkbox to include both SMS/RCS and WhatsApp.
Example text: "By checking this box, you agree to receive notifications via SMS and WhatsApp."
If you don't yet collect SMS or RCS opt-ins:
Add an extra block below the email opt-in checkbox to collect the phone number. Clearly indicate that this number will be used for SMS/RCS and WhatsApp.
Example block:
Field: "Phone number (for SMS and WhatsApp)."
Mention: "By providing your number, you agree to receive our notifications via WhatsApp and SMS."
How to retrieve these opt-ins on the CRM side
Adding this option at checkout should add the customer to a dedicated list in your CRM (for example a "Checkout Opt-in WhatsApp/SMS" list in Klaviyo). This list is what allows WAX to then retrieve the consent information.
This retrieval happens via the "Added to List" event, which you can receive in two ways:
Via webhook, connected directly to your CRM.
Via the Klaviyo integration, which automatically sends this event to WAX.
Tips to optimize collection
Clarity and transparency: explain to users why their number is being collected and how it will be used (WhatsApp and/or SMS/RCS).
Attractive design: make sure the checkboxes and blocks are visually integrated with the rest of the checkout design.
Legal compliance: make sure your messages comply with applicable consent regulations (GDPR, TCPA, etc.).
Find all the other levers:
Some examples :
How to Set Up WhatsApp Opt-in at Checkout on Shopify: