Here is how we think about SMS at Tribe: it is rarely the first thing you reach for, and almost never the only thing. Email does the heavy lifting. SMS is what you add when email alone leaves revenue on the table, usually because a slice of your list simply does not open email anymore.
This is Klaviyo's documented best practice, not a trick we invented. Its Strategist Certificate teaches you to prioritise the channel each customer is most likely to engage with, and its Channel Affinity model predicts that preference from real behaviour so a flow can branch on it with a conditional split. Build it properly and a customer who only ever clicks texts stops getting emails they ignore, and the reverse.
In practice that becomes a waterfall. A flow sends the email first. If the customer does not open it within a set window and the moment still matters, a text follows. For a high-value segment that stays quiet across both, direct mail can catch the ones worth chasing. Each tier costs more than the last, so each one is aimed at a smaller, higher-intent group. The rest of this post is about where SMS fits in that system, what it costs, and when we tell brands not to bother.
Klaviyo SMS or a dedicated platform?
Before the how, the what. You do not have to run SMS through Klaviyo, and two names come up whenever a brand weighs it: Attentive and Postscript.
Both are SMS-first platforms. They tend to lead on list-growth tooling, aggressive sign-up units and, in Attentive's case, a managed-service model aimed at larger senders. If SMS is going to be a primary channel doing serious volume, they are worth a look.
For most DTC brands we work with, though, the case for Klaviyo SMS is the same case as the waterfall itself. It lives in one account with your email, on the same profiles, segments and events. A separate SMS platform means a second data pipe, a second set of consent records and the job of keeping two tools in sync so a customer does not get an email and a text saying the same thing four minutes apart. That coordination is exactly what a waterfall depends on, and it is far easier when both channels read from the same brain. Unless SMS is your headline channel, the integration usually outweighs the extra features a specialist tool brings.
The rest of this post assumes Klaviyo SMS, because that is what suits the brands and the waterfall model we are describing.
What Klaviyo SMS actually is
Klaviyo SMS sits inside the same account as your email programme, drawing on the same profiles, segments and events. That is the whole argument for using it over a standalone texting tool. A customer who opened three emails and bought nothing looks identical in both channels, so you can add a text step to an existing flow and split the audience on behaviour rather than guessing.
It runs in the UK, along with the US, Canada, Australia, New Zealand and a handful of European markets. If you sell across borders, check coverage before you build anything, because a flow that texts UK customers and silently skips everyone else is worse than no flow at all. We cover the wider version of that problem in our guide to Klaviyo setup for international DTC brands.
How Klaviyo SMS pricing works
SMS is billed separately from email, on credits rather than list size. You buy a monthly allowance, each message spends a set number of credits, and the rate varies by destination country and message type. Picture messages cost considerably more than plain text. Long messages split into multiple segments and charge as multiple messages.
This changes the economics in a way that catches brands out. Email costs effectively nothing per send once you are paying for the list, so a mediocre campaign to 40,000 people is merely a wasted opportunity. Send the same mediocre campaign by text and you have spent real money on it. SMS punishes the batch-and-blast habits that email tolerates.
This is also why the waterfall makes financial sense. By the time a message reaches the SMS tier, you are only paying to text people who ignored a free email, not the whole list. The cost lands where the intent is. Work out your cost per send before you commit, then set a revenue-per-recipient floor that a campaign has to clear. If you cannot picture a text that clears it, the channel is not the problem.
UK consent rules are stricter than most SMS guides suggest
Nearly every Klaviyo SMS guide online is written for a US audience, where the rules are set by a different regime entirely. If you sell to UK customers, marketing texts fall under PECR, the Privacy and Electronic Communications Regulations, with UK GDPR governing the data behind them. Copying an American playbook is how brands end up with a list they cannot legally message. What follows is the UK position, which is the one that matters for most of the brands we work with.
Consent has to be specific to SMS
A customer who ticked a box to receive emails has not agreed to receive texts. Consent must be given for the channel, freely, and through a positive action rather than a pre-ticked box or a buried line in your terms. Collecting a phone number at checkout for delivery purposes gives you no marketing permission whatsoever.
The soft opt-in is narrower than people think
PECR allows you to market to existing customers without fresh consent, but only where you obtained the number during a sale or negotiation, only for similar products, and only if you offered a simple refusal at the point of collection and in every message since. Miss any part of that and the exemption does not apply.
Every message needs an identity and an exit
Recipients must be able to tell who is texting them and stop it easily, at no cost beyond the message itself. In practice that means your brand name in the body and a working keyword opt-out, honoured immediately. Klaviyo handles the mechanics, but the wording is yours and so is the liability.
Selling into the EU or US changes the picture
If your list crosses borders, the rules travel with the recipient, not with you. EU customers sit under ePrivacy and GDPR, which broadly mirror the UK on consent, so a UK-clean setup usually holds, though individual member states add their own wrinkles. The US is looser on paper but stricter on the mechanics that get brands sued: prior express written consent for marketing texts under the TCPA, plus quiet-hours and opt-out handling that carry real penalties. Klaviyo can segment by region, so the practical answer is to hold each market to its own standard rather than the loosest one.
Get this right at collection and the rest is straightforward. Get it wrong and you build a list you have to throw away, which is a genuinely expensive mistake. Our guidance on Klaviyo sign-up forms covers how to capture phone numbers alongside email without wrecking form conversion.
Where SMS earns its place
The pattern across the accounts we run is consistent. SMS pays when the message is time-critical and the customer already wants it. It loses money when it duplicates something an email was going to say anyway. In the waterfall, these are the moments where the second tier is worth firing.
Abandoned checkout
The strongest single use case. A short text an hour after abandonment, placed after the first email for people who did not open it, catches customers who left because their hands were full rather than because they changed their mind. Keep it to one send. A second abandoned-checkout text reads as pestering.
Back in stock and low stock
Someone who asked to be told the moment a product returns has told you exactly what they want and when. Speed decides whether they buy, and a text beats an inbox that gets checked twice a day. This is the one flow where SMS routinely outperforms its email equivalent on revenue per recipient, which is why we often let it lead rather than follow.
Upcoming subscription charges
For subscription brands this is the flow worth building first. A text three days before the next charge, linking straight into the customer portal to swap, delay or skip, prevents the cancellation that a surprise payment triggers. It also puts you ahead of the DMCC Act, whose subscription rules will require renewal reminders from Spring 2027.
Pause and swap prompts do more for retention than discounting ever will, and they cost nothing beyond the send. There is a fuller treatment of the mechanics in our subscription retention strategy guide and in Klaviyo flows for subscription brands.
Genuine urgency, used rarely
Early access for a VIP segment, the last day of a sale, a launch with limited stock. These work precisely because they are rare. Brands that text every promotion train their list to ignore them, and unlike an unopened email, an ignored text still cost you money.
When to skip SMS
Three situations where we advise clients against it, at least for now.
If your email programme is underbuilt, fix that first. A brand running four flows and no segmentation has far more revenue sitting in email than SMS will ever return, at a fraction of the cost and none of the compliance exposure. There is no point building the second tier of a waterfall when the first tier leaks. Start with the core Klaviyo flows and come back to SMS once they are earning.
If your average order value is low and your margin thin, the maths rarely works. Every send has a hard cost, so a £22 order with 30% margin leaves very little room once you have texted a few thousand people to get it. High-AOV and subscription brands absorb the cost far more comfortably.
And if you cannot collect consent cleanly, do not start. A phone list gathered through a competition entry or a pre-ticked box is a liability sitting in your account, not an asset.
Setting it up properly
Start by adding phone capture to your existing forms as a second step rather than a required field, so email sign-up conversion holds. Ask separately, explain what they will get, and be specific about frequency.
Build one flow, not six. Abandoned checkout is the usual candidate. Add the SMS tier after the first email, gated on non-open and SMS consent, run it for a month against the email-only version, compare revenue per recipient net of send cost, and only then add a second.
Set a quiet-hours window and respect it. Texting someone at 8am on a Sunday buys you an unsubscribe and, occasionally, a complaint. Klaviyo will hold sends inside a schedule you define, so define one.
All of this assumes your data is flowing correctly in the first place. If Shopify events are not landing in Klaviyo cleanly, the whole waterfall mistimes. Our guide to a properly built Klaviyo and Shopify integration covers what that looks like.
Klaviyo SMS FAQs
Should I run SMS through Klaviyo or a platform like Attentive?
For most DTC brands, Klaviyo SMS wins because it shares one account, one set of profiles and one consent record with your email programme, which makes coordinated email-and-SMS flows straightforward. Dedicated platforms like Attentive or Postscript offer stronger list-growth tooling and suit brands where SMS is a primary, high-volume channel rather than a supporting one.
Is Klaviyo SMS available in the UK?
Yes. Klaviyo SMS supports the UK alongside the US, Canada, Australia, New Zealand and several European markets. Brands selling into multiple regions should confirm country coverage before building flows, because unsupported markets are skipped rather than flagged, which leaves segments of customers receiving nothing while the flow reports as running normally.
How much does Klaviyo SMS cost?
SMS is billed on credits, separately from your email plan. You buy a monthly allowance and each message spends credits at a rate set by destination country and message type, with picture messages costing more than plain text and long messages splitting into multiple charged segments. Calculate your cost per send before committing to the channel.
Do I need separate consent for SMS in the UK?
Yes. Under PECR, consent must be specific to the channel, so an email opt-in does not cover marketing texts. A limited soft opt-in exists for existing customers where the number was collected during a sale, the products are similar, and a simple refusal option was offered at collection and in every message afterwards.
Which SMS flow should a DTC brand build first?
Abandoned checkout for most brands, and upcoming subscription charge reminders for subscription businesses. Both catch customers at a moment when timing decides the outcome and the message is genuinely wanted. Build one, measure revenue per recipient net of send cost against the email-only version for a month, then decide whether to add another.
SMS is a supporting act, not a headline. Build a strong email programme first, add SMS as the second tier of a waterfall for the moments where an inbox is too slow, collect consent cleanly, and measure every send net of its cost. Done that way, it lifts a retention programme without annoying the list that funds it. If you want to see the email work that sits underneath it, our Klaviyo agency results break down what a rebuilt flow architecture did for Kavee across its UK and US accounts, our subscription flows guide covers the Ditto Daily campaign performance, and our retention service shows how email and SMS fit together across a full programme.