Why SMS Compliance Matters in 2025

SMS remains one of the highest-ROI channels for e-commerce, boasting 90%+ open rates and unmatched engagement. However, it’s also one of the most tightly regulated, especially as of 2025.

New updates from the CTIA and TCPA require stricter compliance. Brands must now provide clear proof of consent, use verified opt-in methods, and offer easy opt-out options in every message. International laws, such as GDPR (EU/UK), CASL (Canada), and CAN-SPAM (US), add extra layers, requiring lawful messaging, regional disclosures, and secure data handling.

Klaviyo helps simplify compliance across markets with built-in consent fields, double opt-in flows, quiet hour controls, and automated unsubscribe handling, so you can grow your SMS list with confidence.

In this 2025 guide, you'll learn:

• The core SMS laws by region

• How to collect and store valid consent in Klaviyo

• Mistakes to avoid that could lead to fines or blocked sends

• How to audit and maintain your compliance setup

• Practical tips to stay legal and drive results

Understand the 2025 SMS Compliance Rules

In 2025, SMS is more regulated than ever. Each region has strict laws, and Klaviyo helps you stay compliant by tracking consent, supporting opt-outs, and managing regional requirements.

Key Laws You Must Know:

Collecting Proper SMS Consent

Without clear consent:

• Your SMS messages may be blocked by carriers before reaching customers.

• You risk fines, penalties, or lawsuits ,  especially in the US and Canada.

• Customer trust can decline if messages feel invasive or unexpected.

Klaviyo’s role:

Klaviyo automatically logs consent metadata (IP address, timestamp, source) and links it to each subscriber’s profile, so you can prove opt-in at any point.

Compliant Opt-In Methods

Here are three accepted ways to collect valid SMS consent using Klaviyo:

On-Site Forms

• Use Klaviyo's form builder to include an unchecked SMS opt-in box.

• Include clear disclosure language (e.g. “By signing up, you agree to receive texts…”)

• Optional: Link to your privacy policy for transparency.

Checkout Opt-In

• On platforms like Shopify, Klaviyo syncs SMS checkboxes into the checkout flow.

• Ensure the checkbox is not pre-selected and includes disclosure.

• Klaviyo captures consent metadata (timestamp, IP, and opt-in source) automatically.

Keyword Opt-In via SMS (Single vs Double)

• A user texts a keyword (e.g. JOIN) to your number.

• Use Klaviyo to trigger a double opt-in flow confirming consent before sending marketing texts.

• This method is preferred under CTIA 2025 rules, as it creates a validated audit trail.

Forms That Do Not Comply

Source:  Klaviyo Help Centre – SMS Consent, Klaviyo Compliance Guide

If you're unsure how to structure your pop-ups or embed forms correctly, our breakdown of Top 8 Klaviyo Pop-Up Form Strategies includes compliance-ready tips to boost conversions without risking violations.

The 7 Compliance Basics for SMS (2025)

Follow these 7 key rules to stay compliant and protect your ROI with Klaviyo SMS:

1. Always Get Consent

Only send SMS to users who’ve explicitly opted in. Klaviyo logs consent with timestamp, method, and IP. Use double opt-in for keyword flows.

2. Easy Unsubscribes

Every message must include a clear opt-out (e.g. “Reply STOP”). Klaviyo auto-handles STOP/HELP replies and updates profiles instantly.

3. Avoid Prohibited Content

Blocklisted topics include hate speech, adult content, false claims, and illegal offers. Klaviyo flags risky language and failed sends.

4. Respect Quiet Hours

Don’t text before 8 am or after 9 pm local time (per TCPA/CTIA). Enable “Quiet Hours” in Klaviyo to automate safe delivery windows.

5. Identify Your Brand

Include your brand name in every SMS. Use Klaviyo dynamic tags or set it manually in templates.

6. Abandoned Cart Consent (US)

You must get separate SMS consent for cart reminders, email permission doesn’t count. Add a clear SMS checkbox at checkout in Klaviyo.

7. Canadian-Specific Rules (CASL)

SMS to Canadian users must include sender info, mailing address, and opt-out wording. Use Klaviyo segmentation to tailor messages by country.

For more on building compliant and effective abandonment flows, check out our Klaviyo’s SMS Abandoned Cart: The Ultimate Guide.

Enable SMS & Configure Compliance in Klaviyo

Make the compliance setup smooth and aligned with Klaviyo’s process:

1. Navigate to SMS Settings

• Go to Settings > SMS & MMS in your Klaviyo dashboard.

• Click Set Up SMS to begin the activation process.

  
  

2. Enable Compliance Settings

• Toggle Consent Tracking to automatically log consent sources, timestamps, and IP addresses.

• Turn on Quiet Hours to prevent messages from sending outside legal time windows (typically 8am–9pm local time).

  
  

3. Configure Opt-In Settings

• Under Opt-In Settings, choose your default keyword (e.g. JOIN) and set up a double opt-in flow to ensure legal consent.

• You can customise confirmation messages to match CTIA/TCPA formatting requirements.
  
  

4. Set Up Opt-Out and HELP Flows

• Klaviyo provides default STOP and HELP flows, review these and customise the response messages to reflect your brand tone and compliance.

  
  

5. Test Before You Send

• Create a dummy profile to test opt-in, confirmation, and opt-out actions. Ensure SMS messages are only sent after proper consent is logged.
  
  
  

6. Use Klaviyo Forms or Custom Integrations

• For website or checkout collection, use Klaviyo’s native form builder with an unchecked SMS checkbox and consent language.

• Alternatively, sync third-party platforms via Zapier or API, ensure these sources track opt-in data correctly.

Ongoing Compliance Best Practices

Maintaining compliance in Klaviyo isn’t just a one-off setup. Regular audits and hygiene help protect deliverability, improve customer trust, and ensure legal alignment across SMS and email.

Monthly Compliance Audit Checklist

Consent Capture

• Confirm all live sign-up forms (pop-ups, embedded) use Klaviyo’s sms_consent and email_consent fields.

• SMS checkboxes must be unchecked by default.

Disclosure Language

• Review and update SMS disclosure language (e.g. carrier fees, opt-out terms).

• Ensure your Shopify or third-party pop-ups also include compliant copy.

STOP & HELP Reply Flows

• In Klaviyo > Settings > SMS > Compliance, verify that STOP/HELP replies trigger the correct automated responses.

• STOP should remove SMS consent and HELP should return support contact info.

Quiet Hours & Logging

• Confirm Quiet Hours are still enabled (e.g. 8pm–8am local time).

• Review consent logs in Klaviyo for opt-in and opt-out activity tracking.

List Hygiene & Consent Maintenance

Clean Inactive or Invalid Profiles

Use engagement filters to identify and suppress:

• Hard-bounced emails or phone numbers

• Opt-outs still receiving sends

• Profiles missing valid sms_consent or email_consent

Reconfirm Consent for Cold Profiles

• Create re-permission campaigns for profiles inactive for 90–180+ days.

• Use Klaviyo forms or quizzes to collect updated preferences.

• To re-engage unresponsive contacts effectively and lawfully, follow the principles in our Winback Flow: 6 Tips To Re-engage Lapsed Customers blog and pair it with updated consent prompts.

Recollect Consent After Policy Changes

• If you change terms or messaging frequency, trigger double opt-in or re-opt-in flows.

• Segment profiles who haven’t accepted the new policies for targeted re-engagement.

Exclude Risk Segments

Build auto-updating segments such as:

• Subscribed but never clicked in 180+ days

• Imported profiles missing signup source

• SMS recipients with no logged consent

Common SMS Compliance Mistakes (And How to Avoid Them)

Even the most well-meaning brands can fall foul of SMS compliance laws. Here are the most common mistakes, the risks they carry, and exactly how to fix them using Klaviyo's native tools and setup recommendations.

Even small oversights can snowball into major issues, our breakdown of 15 Top Email Marketing Mistakes to Avoid applies to SMS as well, especially around consent, frequency, and personalisation.

Troubleshooting Compliance Issues in Klaviyo

Even with proper setup, issues can occur. Here’s how to quickly resolve common SMS compliance problems:

1. Message Failed: “Unauthorised Opt-In”

• Cause: Missing consent.

• Fix: Ensure $consent.sms = true is captured via Klaviyo form or API sync with timestamp.

2. Message Not Delivered

• Cause: Consent not granted for SMS or contact only opted into email.

• Fix: Confirm consent property exists and use Klaviyo's consented import templates.

3. SMS Not Sending

• Cause: Blocked by quiet hours, Smart Sending, or missing consent.

• Fix: Check profile for valid phone number + consent, and review sending rules.

• Sometimes, SMS delivery issues stem from incorrect list setup. Learn how to avoid these pitfalls and track your results using Klaviyo UTM Tracking.

4. High Unsubscribes

• Cause: Messaging too often or irrelevant content.

• Fix: Limit sends, segment by engagement, and review copy/timing.

FAQs

1. Can I collect SMS consent through a pop-up form on mobile?

• Yes, but ensure the checkbox is not pre-ticked, and all disclosures are visible without needing to scroll.

2. What’s the difference between single and double opt-in for SMS?

• Single opt-in only captures the initial sign-up. Double opt-in requires users to confirm via reply or link, offering stronger proof and lower compliance risk. For campaigns that rely on high-intent engagement, double opt-in can significantly improve your click metrics—learn more in our article on Klaviyo Predictive Analytics.

3. Do I need separate consent for transactional vs promotional SMS?

• Yes. Transactional texts (like shipping updates) can be sent with implicit consent, but marketing texts always need explicit opt-in.

4. Can I send SMS to users who subscribed via another platform?

• Only if that platform passes valid consent data (timestamp, source, opt-in type). You must import using Klaviyo’s compliant formatting.

5. Does Smart Sending replace Quiet Hours?

• No. Smart Sending avoids over-messaging but does not restrict messages by time of day. You should enable both for full compliance.

Conclusion

SMS marketing can drive powerful results, but only when it's built on trust, permission, and legal clarity. With new 2025 regulations tightening enforcement, staying compliant isn’t optional, it’s essential. 

Whether it’s using Klaviyo’s built-in consent tools, avoiding pre-checked boxes, or setting quiet hours, every step protects your brand and improves your customer experience. Focus on clarity, consent, and care, and your SMS program will be stronger, safer, and more profitable.

Key Takeaways

• Know the Laws: Understand TCPA, CTIA, GDPR, and CASL requirements per region.

• Use Klaviyo Tools: Set up consent tracking, quiet hours, and STOP/HELP flows natively.

• Collect Proper Consent: Avoid pre-ticked boxes, use disclosures, and enable double opt-in.

• Audit Regularly: Check SMS forms, flows, quiet hours, and list hygiene monthly.

• Fix Common Errors: Resolve issues like missing timestamps, delivery failures, and high opt-outs fast.

Is your Klaviyo SMS strategy fully compliant? 

Avoid fines and deliver better experiences by aligning with 2025’s latest global SMS regulations. Click here to get a free compliance audit with our experts today.