How to set up a successful back in stock flow in Klaviyo

When a popular product is temporarily out of stock, are you losing revenue? Not if you handle it smartly. With a well-designed back in stock flow in Klaviyo, you can automatically notify interested customers as soon as the product is back. No extra ads, no pressure, just results.

At Pinelab, we’ve implemented this flow for multiple clients. Within 24 hours of going live, we saw the first conversions come in. In this post, we’ll explain why this flow works so well, how to set it up, and what to keep in mind.

What is a back in stock flow?

A back in stock flow is an automated email (or SMS) sent to customers who signed up to be notified when a product is back in stock. Once the product is available again, they get a message automatically.

It may sound simple, but the impact is huge. You're connecting with people while their interest is still fresh. And since they opted in themselves, the likelihood of conversion is much higher than with a regular newsletter or remarketing campaign.

How a back in stock flow works in Klaviyo

The flow has three key components:

The trigger on your product page
Customers can sign up via a “Notify me when available” button.

At Pinelab, we built an automatic integration to handle this:
- When a product in Vendure goes out of stock, the signup form is automatically shown on the product page. Each signup is stored with the product ID from your feed. This is essential: when stock updates come in, Klaviyo knows exactly which product the customer was interested in, making the automation accurate and reliable.
- Once the product is back in stock, Klaviyo gets updated.
- The flow then automatically sends a notification to everyone who signed up.
The automation in Klaviyo
You can expand the flow with conditions like “minimum stock available,” or segment based on customer behavior.
The email itself
Keep it short, personal, and urgent. Include product visuals, show how many are available, and make it easy to buy right away.

Example of the back in stock subsription.

What results can you expect?

For one of our clients working in biodiversity restoration, we saw the first back order purchases come in the very next day.

Because interest has already been validated, these flows often see:

open rates of 60%+
CTRs over 20%
conversion rates similar to winback campaigns

And the best part? These flows run entirely on autopilot.

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Best practices from the field

Set a minimum stock threshold
Only trigger the message when you have, say, 10 or more items in stock—this avoids customer frustration.
Use urgency, but keep it honest
If there are only a few left, say so. But don’t exaggerate, authenticity always wins. (I see you Booking.com)
Segment wisely
Consider treating returning customers differently from new ones, or prioritize B2B customers where applicable.

Using back order data for inventory planning

One underestimated benefit of back in stock flows is the data you collect. Every signup gives you insight into:

Which variants (e.g. sizes, colors) are in demand
Anticipated repeat demand
Whether it’s viable to restock or even offer pre-orders

By feeding this data back into your inventory team, you’ll avoid reacting too late. This is especially valuable if your production chain is sustainable, slow-made or circular, back order interest is a powerful signal for smarter planning.

In summary

A well-executed back in stock flow in Klaviyo helps you recover lost revenue through automated, meaningful engagement. Especially for brands that work mindfully with inventory and production, this is a high-impact, low-effort win.

Curious how this Klaviyo back in stock flow would work for your brand? Or want to integrate it directly with your e-commerce stack? We’d love to help.

Book a free e-commerce online marketing strategy session