How to Build a Compliant Abandoned Cart SMS Flow in Postscript

An abandoned cart SMS is one of the highest-converting automated messages a Shopify store can send, precisely because it reaches someone at the exact moment of highest purchase intent. That same immediacy is why getting the compliance groundwork wrong here is especially costly: this flow sends automatically, at volume, to people who just interacted with a checkout form, which is exactly the kind of pattern that draws scrutiny if the underlying consent or send behavior isn't actually correct. Here's the setup that gets both the recovery mechanics and the compliance right.

For background on what Postscript is, its pricing, and how it compares to Attentive, see our full Postscript profile. And our piece on why federal TCPA compliance alone no longer covers an SMS program covers the state-law landscape this flow needs to respect.

Step 1: Complete 10DLC Registration Before Building Anything Else

10DLC registration, the carrier system required to send business SMS in the US, typically takes one to three business days for approval, and Postscript guides merchants through it during onboarding. Start this process before building the flow itself, not after, since a fully built abandoned cart sequence sitting behind an unapproved sending number is a flow that can't actually go live on the timeline a launch plan usually assumes.

Step 2: Build a Genuinely Compliant Opt-In Capture, Not Just a Checkbox

Set up the opt-in flow with explicit, unchecked-by-default consent (the shopper has to actively check a box or reply to a keyword, never a pre-checked default), clear disclosure of what they're agreeing to (automated marketing texts, roughly how often, and that consent isn't a condition of completing their purchase), and, per current requirements, a double opt-in step, an initial consent action followed by a confirmation reply before promotional messages begin. This is the step most likely to get rushed because it happens once at signup rather than being visible in the abandoned cart flow itself, but it's the consent record that everything downstream, including the abandoned cart sequence, legally depends on.

Step 3: Trigger the Flow Off the Cart-Abandoned Event, Not a Fixed Schedule

Connect the flow to fire off an actual cart-abandoned event from the store, via Postscript's Shopify integration, rather than a manually scheduled batch send. This keeps the timing tied to when a specific shopper actually abandoned their cart rather than an arbitrary daily send window, which matters both for conversion (a same-day, event-triggered message consistently outperforms a delayed batch send) and for the frequency-cap compliance question, since an event-triggered single message is easier to reason about against a state's per-day message cap than a batch send layered on top of other campaign activity.

Step 4: Set the First Message to Fire Within 15 to 30 Minutes

Configure the flow's timing so the first message sends roughly 15 to 30 minutes after abandonment, while purchase intent is still fresh, rather than delaying by hours. Waiting too long trades away most of the recovery value this flow is built to capture, since a shopper who abandoned a cart is also actively free to keep shopping elsewhere, or simply lose the specific intent that made the product feel worth buying in that moment.

Step 5: Keep the Message Short, Specific, and Under 160 Characters

Write the message to include the shopper's name, the specific product they left behind, and a direct link straight back to their cart, kept under roughly 160 characters so it renders as a single SMS segment rather than splitting across multiple messages. A generic "you left something in your cart" message converts meaningfully worse than one referencing the actual product by name, and the direct cart link removes friction that would otherwise cost conversions between the tap and the completed checkout.

Step 6: Add One Follow-Up, Then Stop

Add a single follow-up message roughly a day after the first, optionally including a modest incentive to close the sale, and end the sequence there rather than continuing to message a shopper who hasn't responded. This isn't just a conversion best practice, it's also the frequency discipline that keeps the flow well inside even the stricter state caps like Florida's three-message-per-24-hours limit on a single topic, since two total messages spread across two days is comfortably within that boundary in a way a longer, more aggressive sequence might not be.

Step 7: Confirm Quiet Hours and Keyword Handling Are Actually Active

Postscript applies quiet-hours restrictions and automated STOP/HELP keyword handling by default, but confirm these are active and correctly configured for this specific flow rather than assuming default settings automatically cover every use case. Quiet hours matter specifically for a triggered flow like this one, since cart abandonment can happen at any hour, and an automated send firing at 2am recipient time is exactly the kind of pattern a stricter state law is built to catch, regardless of how well the message itself converts when it lands at a reasonable hour.

Step 8: Test the Full Flow End to End, Including Opt-Out

Before going live, run through the entire flow as a real shopper would: abandon a test cart, confirm the timing and message content render correctly, and specifically test that replying STOP actually halts future messages to that number. A flow that converts well but has a broken or delayed opt-out mechanism turns a working recovery sequence into a compliance liability the moment a real customer tries to unsubscribe and keeps receiving messages anyway.

A Few Mistakes That Undo This Setup

A handful of habits reliably turn a well-converting flow into a compliance liability. Launching before 10DLC approval completes, or before the double opt-in confirmation is actually wired up correctly, means the flow is sending on a consent foundation that isn't actually in place yet, regardless of how well the message itself converts. Extending the sequence to three or four follow-up messages because early data shows each additional touch recovers a few more carts ignores that the recovery math has to be weighed against frequency-cap exposure in stricter states, not evaluated purely on conversion lift. And treating the quiet-hours and keyword-handling defaults as permanently correct without ever testing them directly on this specific flow means a configuration issue could go unnoticed for months, since nothing about a well-converting flow announces that its compliance settings have drifted.

What This Workflow Actually Produces

Built this way, an abandoned cart SMS flow captures the real recovery value SMS is known for, fast, personalized, high-intent timing, without carrying the compliance risk that comes from treating consent and frequency as an afterthought behind the conversion mechanics. That's a meaningfully more durable setup than a flow optimized purely for recovery rate with the compliance groundwork assumed rather than verified, and it's the difference between a flow that performs well until a state-level complaint surfaces and one built to hold up regardless of which state the message happened to land in.

It's worth treating this flow specifically, rather than every SMS automation equally, as the one to get right first. It's typically the highest-volume automated sequence a Shopify store runs, triggered by real-time behavior rather than a scheduled campaign, which means any compliance gap in its setup compounds continuously across every abandonment event rather than surfacing once and getting caught. Getting the opt-in, timing, frequency, and quiet-hours configuration right here, specifically, is a disproportionately good use of setup time relative to the flow's typical share of total program volume, and it's a template worth reusing, not reinventing, when the same discipline gets applied to back-in-stock, post-purchase, or win-back sequences later.

If you're still deciding whether Postscript's Shopify-exclusive focus fits your store versus a platform like Attentive, our Postscript tool profile and Attentive vs Postscript comparison cover the pricing and feature tradeoffs in more detail.