An abandoned cart text works best as a single personal message sent about an hour after the cart is left: by SMS in the US, with prior express written consent under the TCPA, or by WhatsApp in Europe and Latin America, through the WhatsApp Business Platform (not the free app), a Meta-approved template and a specific opt-in.
The channel depends on where your customers are. In the United States, text messaging means SMS; in much of Europe and Latin America, people live in WhatsApp, and that is where a cart reminder feels natural. The rules below are mostly about WhatsApp, because it has the most moving parts, with the SMS differences flagged where they matter. You will find the two versions of WhatsApp Business, how templates and costs work, what Meta, the FCC and EU regulators expect on consent, and how to collect it on Shopify and Klaviyo. At the end, the text message inside the cart recovery flow, with two example messages.
WhatsApp Business app or Platform: which one an online store needs
The WhatsApp Business app is the free phone application: business profile, catalog, quick replies. Apart from the greeting and away messages, everything is manual, and broadcast lists top out at 256 contacts. It is fine for answering customers and not built for the marketing of an online store.
The WhatsApp Business Platform (often called the "API") is the version that connects to other systems, through a provider authorized by Meta or a platform that integrates it, such as Klaviyo. It is the only one that can start a message from a store event, like an abandoned checkout, and manage consent customer by customer. To connect WhatsApp to an ecommerce store, the answer is always the Platform.
Templates, the 24-hour window and costs
When a customer writes to you, a 24-hour service window opens, during which you can reply with free-form messages at no charge. Outside that window you can only send templates: message models with variable parts (name, product, link) that Meta approves before use.
Templates come in three categories: marketing, utility and authentication. Utility messages are non-promotional and tied to something the customer did, such as an order confirmation or tracking update. A cart reminder, under Meta's rules, is marketing: it counts as retargeting, even though the customer started the purchase. A utility template that contains a promotion is treated as marketing.
On costs, since July 1, 2025 Meta no longer charges per conversation but per template message delivered. The rate depends on the category, your monthly volume and the country code of the recipient. Marketing templates are always charged; utility templates are free when sent inside an open service window. For current figures, check Meta's rate card for your market; your provider may add its own fee.
Consent: what Meta, the TCPA and EU regulators require
For SMS in the US, the FCC's rules under the Telephone Consumer Protection Act (47 CFR § 64.1200) require prior express written consent before a seller sends advertising or telemarketing messages with an autodialer. That means an agreement in writing, with the customer's signature (an electronic one counts), that clearly authorizes marketing texts to a specific number. It must also state that signing is not a condition of buying anything. Consent buried in terms of service does not meet that standard, and a cart reminder is marketing, so it falls under it.
Meta adds its own rules for WhatsApp: the opt-in must say clearly that the person agrees to receive messages and from which business, and the store must comply with local law. Customers can block or report a sender, and Meta limits sending for businesses that keep a low quality rating for a long time.
In the EU the cart reminder is marketing and needs prior consent; Italy's authority, for example, applies the same rules to messaging apps as to email. Having a phone number for delivery is not enough, and neither is finding it online. In every market, a checkbox dedicated to the channel, with the store's name in the text, is the cleanest approach. None of this replaces advice from your own privacy or legal counsel.
How to collect consent on Shopify and Klaviyo
In Klaviyo, WhatsApp consent is recorded separately from email and SMS: a profile can have one, the other, both or neither. There are three ways to collect it.
- Klaviyo signup form: a dedicated step for the phone number after the email step, with consent text that names WhatsApp (or SMS) and your store.
- Shopify checkout: a Klaviyo app block ("Opt-in at checkout") adds the checkbox. Depending on your Shopify plan, it can sit in the checkout pages or only on the thank-you and order status pages.
- Keyword, link or QR code: the customer messages your store on WhatsApp, which gives the consent.
For cart recovery, consent has to exist before the abandonment. The thank-you page checkbox helps with returning customers; for people who abandon on a first visit, you need the site form or the checkout checkbox.
What to send by text and what to leave out
WhatsApp is where people chat with friends and family, and a message out of place costs you a block. SMS is a similar personal inbox. What works is what the customer expects: cart reminders, order confirmations, shipping updates, replies. What does not: daily broadcasts, generic promotions sent to everyone, chains of nudges. If you want a broadcast list that performs, keep it small and rare, with people who signed up for a specific reason, only when you have something that really concerns them.
| Text message (SMS or WhatsApp) | ||
|---|---|---|
| Reading time | Often hours, alongside other emails | Usually a few minutes |
| Consent | Opt-in rules vary by country | Always a specific opt-in; written consent for SMS in the US; Meta requires it for WhatsApp |
| Cost | Included in the email platform plan | Per message: Meta's rate card by country for WhatsApp, your SMS provider's rates for SMS |
| When to use it | Sequences, newsletters, rich content | One timely, personal message |
Recovering carts by text: timing and messages
The recommended sequence: a text about an hour after abandonment, with the first email pushed back by at least three hours, then the follow-up emails at 24 and 48-72 hours. One text per abandonment, never two; Klaviyo's guide to the abandoned cart flow recommends the same. The sequencing is the same for an SMS step. In a Klaviyo flow you get it with a conditional split on consent: people who can receive WhatsApp marketing get the message, everyone else gets the first email already at one hour.
The tone is that of a personal message, not an ad: name, product, a concrete offer of help, one link. No discount in the first contact. If the customer replies, the 24-hour window opens and the conversation becomes real customer service.
Hi Emily, it's Hannah from Aurora Jewelry. You left the sterling silver hoop earrings in your cart. If you have a question about the size or want them gift-wrapped, just reply here and I'll help. Your cart is still saved: {link}
Hi Mark, the magnesium you picked is still in your cart. If you're wondering how to pair it with vitamin D, message us here: a real person on our team will answer. You can finish your order whenever you like: {link}
In the flows AchillesAI builds with the WhatsApp channel, the email and the message are part of the same Klaviyo flow: WhatsApp goes out at about one hour, the first email moves back by at least three hours, and both are written for the individual customer, with the product they left and in their language. Sending stays in Klaviyo, through a Meta-approved template and only to people who gave consent.
Where to start
First, add a separate consent checkbox to your site form and your checkout, with the store's name in the text. Then create a single marketing template for the cart reminder and slot it into your existing flow, moving the first email back by three hours. Keep broadcasts and promotions off text channels until you see how customers react.
For the full timing, read when to send abandoned cart emails; for email consent, are abandoned cart emails transactional?; for the platform behind the flow, what is Klaviyo, how it works and pricing.
