Klaviyo SMS setup done correctly takes about 4 hours and enables a channel that outperforms email on open rates by 3 to 4 times. Done incorrectly, it creates compliance risk and list quality problems that are difficult to undo. Here is the step-by-step setup for D2C brands in the US.
Prerequisites Before Setup
US SMS marketing is governed by the Telephone Consumer Protection Act (TCPA) and requires explicit written consent from every subscriber before you can send them marketing messages. This is not optional. TCPA violations carry fines of $500 to $1,500 per message to non-consenting recipients. Your consent mechanism, not your SMS content, is the foundation of a legally compliant programme.
10DLC registration: 10-digit Long Code registration is required for US business SMS since 2023. Every business sending marketing SMS must register their brand and campaign with The Campaign Registry (TCR) via their SMS provider. Klaviyo handles this process within their SMS settings. Unregistered numbers have message throughput limited to 1 message per second and face carrier filtering. Registered numbers can send at much higher volume with better deliverability.
Klaviyo SMS Setup Steps
Step 1: Enable SMS in Klaviyo account settings under Channels, then SMS. Follow the 10DLC registration flow, which requires your business legal name, business type, employer identification number (EIN), and a description of your SMS use case. Registration typically takes 1 to 5 business days.
Step 2: Assign a phone number. Choose a long code (10-digit number, lower cost, limited to 1 message per second until 10DLC is approved) or a toll-free number (higher trust signal for consumers, typically faster approval than standard long codes). Most D2C brands start with a long code after 10DLC approval.
Step 3: Set up SMS consent collection. Add an SMS opt-in checkbox to your Klaviyo pop-up form. The checkbox must be unchecked by default (TCPA requirement). The label must include: your brand name, that you will send marketing messages, message and data rates may apply, and a link to your terms and privacy policy. "Get SMS updates from [Brand]. Message and data rates may apply. Reply STOP to unsubscribe." is the required disclosure format.
Step 4: Configure automatic compliance responses. Klaviyo handles STOP, HELP, and UNSTOP keywords automatically. When a subscriber texts STOP, they are immediately opted out and you cannot text them again unless they re-opt-in. Verify this is working correctly by texting STOP from a test number and confirming the opt-out is recorded in Klaviyo.
First SMS Flows to Activate
SMS welcome: send within 5 minutes of opt-in. Under 160 characters. Brand name, their discount or offer, and a direct link. Abandoned cart SMS: 60 to 90 minutes after cart abandonment if the email has not been opened. Two-sentence max. Shipping update: triggered automatically via Shopify order events. High open rate, zero complaints because it is transactional and expected.