Reward customers with a discount code for reviews

01/The build

How to build it

1. 01

   Set the reward, the rules, and the line you won't cross

   Needs a human

   Decide this before automating anything, because it's the part software can't judge. The reward: a modest percentage or fixed amount that's worth a customer's effort without eating the next order's margin — most stores land at 10-15% or a flat few dollars. The guardrails: single redemption, one per customer, a minimum order subtotal so it can't be used on a $4 add-on, an expiry (30-60 days keeps it fresh and limits liability), exclude sale items and wholesale, and no stacking with other codes. And the non-negotiable legal line: you reward an honest review, not a positive one. Never condition the code on the rating, and make sure the incentive is disclosed — the FTC treats an undisclosed incentivized review as deceptive, and most review platforms add an 'incentivized' badge automatically when you tell them a reward is attached. Write all of this down; every step below just enforces it.

2. 02

   Trigger on a verified review, not any review

   Runs itself

   The reward fires off a 'Review Submitted' / 'Reviewed Product' event from your review platform — Yotpo, Okendo, Judge.me, Loox, and Stamped all emit one, either as a webhook or as a metric synced into Klaviyo. The trap is rewarding reviews that have no purchase behind them: a site visitor, or worse, someone who realizes anonymous reviews mint codes and writes ten. Gate the trigger on the platform's verified-buyer flag, and confirm the review carries an order ID and a real customer. No verified order, no reward. This single filter is what stops the automation from becoming a code printer for fake reviews.

3. 03

   Check you haven't already rewarded this review

   Runs itself

   Before minting anything, look up whether this specific review has already paid out. Key off the review's unique ID — not the customer, and not the order, because a customer can legitimately review several products from one order and a review can be edited later, which re-fires the event. Keep the issued review IDs in a place a re-run can read: a customer metafield (e.g. a JSON list under custom.rewarded_review_ids), a tag, or an Airtable row. If this review ID is already on the list, stop. Idempotency keyed to the review ID is what keeps an edited review or a duplicate webhook from minting a second code.

4. 04

   Mint a unique, single-use code in Shopify

   Runs itself

   Call the Shopify Admin GraphQL API's discountCodeBasicCreate mutation to create one fresh code per review — generate a readable, unguessable code like THANKS-7QF2K rather than a reusable word. Set the fields from step one explicitly: usageLimit: 1 and appliesOncePerCustomer: true (both, so it dies after a single redemption), startsAt/endsAt for the expiry, a minimumRequirement subtotal, the value as a percentage or fixed discountAmount, and combinesWith with productDiscounts/orderDiscounts/shippingDiscounts all false so it can't be stacked. Read back the created code and ID from the mutation response — you'll need them in the next two steps.

5. 05

   Lock the code to the reviewing customer

   Runs itself

   Set customerSelection on the discount to that one customer (customers.add: [customerId]) instead of leaving it open to everyone. This is the difference between a private reward and a public coupon: a code restricted to a customer ID can't be redeemed by whoever screenshots it onto a coupon extension or a deals forum, so the margin you're spending actually goes to the person who did the work. If you'd rather the code be giftable, you can leave it open and lean on the single-use limit instead — but for a review reward, customer-locked is the safer default and the one worth keeping.

6. 06

   Record the code and review ID so it can't fire twice

   Runs itself

   The moment the code is created, write the review ID — and the code itself — back to the idempotency record from step three (the customer metafield, tag, or Airtable row). Completing this write immediately, before the email send, closes the gap where a crash or a retry mid-flow could mint a second code for the same review. This record is also your audit trail: which review earned which code, when it expires, and whether it's been redeemed when you reconcile against Shopify's discount usage later.

7. 07

   Hand the code to Klaviyo and let a flow send it

   Runs itself

   Fire a custom 'Review Reward Issued' event to the customer's Klaviyo profile with the code, the discount value, and the expiry date as event properties, then trigger a thank-you flow off that event. Letting Klaviyo own the send means consent, quiet hours, and unsubscribes are all respected automatically — far safer than a raw API email that ignores them. Keep the email honest and short: thank them for the specific product they reviewed, show the code and its expiry plainly, and don't dress a 10% code up as a 'VIP exclusive.' If they consented to SMS and that's their channel, send it there instead.

8. 08

   Watch for refunds and abuse after the fact

   Needs a human

   Two edge cases the up-front filter can't catch. First, a customer can review, collect the code, then return the order — decide your policy and enforce it: most stores let a small reward stand, but if you want to claw it back you can deactivate an unredeemed code via the API when a refund posts. Second, abuse patterns: many reviews from one account in a short window, or a spike in review-triggered codes, should post to a Slack channel for a human to glance at rather than paying out silently. Everything else runs untouched; these two are the cases worth a person's eyes.

02/The stack

What it’s built on

Shopify

Where the code is minted and where it lives. The Admin GraphQL API's discountCodeBasicCreate mutation builds each single-use, customer-locked code with the usage limit, expiry, minimum, and no-stacking rules; Shopify also tracks redemption, which is how you reconcile rewards against revenue later.

Klaviyo

Owns the delivery. The 'Review Reward Issued' event triggers a thank-you flow that sends the code while respecting consent, quiet hours, and unsubscribes. The review signal it can also trigger from comes through your review platform's native Klaviyo integration.Klaviyo's free tier covers building and testing this, and you're almost certainly already running it for email. Any ESP that accepts a custom event with properties can deliver the code the same way — only the event API shape changes.

n8n

The glue between the two: it catches the verified-review event, runs the dedupe check, calls the Shopify mutation to mint the code, writes the idempotency record, and fires the Klaviyo event.Before building this, check whether your review platform already does it natively — Loox, Judge.me, and Yotpo all have a built-in 'reward a coupon for a review or photo' feature that's free and made for exactly this. n8n (open-source and self-hostable; their cloud tier just saves you hosting) is the right tool when you've outgrown the native version — you want Shopify-native single-use codes, per-customer locking, margin guardrails the built-in feature won't enforce, or you're consolidating across more than one review tool. Zapier can do the same wiring if you'd rather not host anything.

03/Questions

Before you build