Integrating Flex with RevenueCat

Overview

Flex integrates with RevenueCat to help you manage subscriptions seamlessly across platforms. This guide walks you through connecting your RevenueCat account to Flex, passing a stable customer identifier, saving the integration, and understanding how events map between systems.

Installation Guide

Add RevenueCat in Flex

Log in to your Flex Dashboard.Go to Integrations → RevenueCat.Enter your RevenueCat App ID and API Key.

You can find these in your RevenueCat project under App Settings.

Configure in RevenueCat

In your RevenueCat project, open the Apps section.Click + Add and select Other payment provider.Copy your App ID and Secret API Key.Paste these values into the Flex Dashboard RevenueCat fields from Step 1.

RevenueCat “Apps” page showing Other Payment Provider selected

If you don’t see “Other payment provider (External source)” in your RevenueCat Apps page, that option may not be enabled for your project.Please contact RevenueCat Support and ask them to enable the External payment provider integration for your project.Include:

Your Project ID / link
The App name
That you want to connect Flex as the external payment provider

Pass a Custom User Identifier to RevenueCat

If you want RevenueCat to reference your own user ID (or a Flex user ID), include it in the checkout session metadata as REVENUE_CAT_CUSTOMER_ID.

{
  "checkout_session": {
    "line_items": [
      {
        "price": "fprice_01k2j2zfnbrs5e0r4c8wqphv29",
        "quantity": 1
      }
    ],
    "success_url": "https://example.com/thank-you?success=true",
    "mode": "subscription",
    "cancel_url": "https://example.com/thank-you?canceled=true",
    "shipping_address_collection": false,
    "defaults": {
      "first_name": "Varsha",
      "last_name": "Parthay",
      "email": "rclivedemo1@gmail.com"
    },
    "metadata": {
      "REVENUE_CAT_CUSTOMER_ID": "1234567890"
    }
  }
}

Save and Sync

Click Save in the Flex Dashboard integration page.Flex will begin sending subscription events to RevenueCat so customer status stays in sync.

Tip: If you have existing subscriptions, run an initial sync (or perform a backfill) so historical subscriptions are recognized in RevenueCat.

How Flex Integrates with RevenueCat

There are two ways subscriptions can flow into RevenueCat:

Native Stripe Integration

Stripe sends webhooks directly to RC. RC processes them and generates events with store: "STRIPE".

Flex External Purchases API

Flex processes payments via Stripe, then syncs subscription state to RC via the External Purchases API (POST /v1/receipts/external). RC generates events with store: "EXTERNAL".

For Flex-managed subscriptions, all events come through the External Purchases API path. The subscription data is accurate and revenue is correctly tracked — but certain webhook fields have different values than a native Stripe integration would produce.

If you’re migrating from a native Stripe → RevenueCat integration, be aware of these key differences:

store is "EXTERNAL", not "STRIPE" — update any webhook consumers that filter by store
Refund events have price: 0.0, never negative — use the RC Subscriber API or Flex API for refund amounts
expiration_reason is always null — use cancel_reason on preceding CANCELLATION events instead
Prorated refunds are invisible in webhooks — no CUSTOMER_SUPPORT event is generated; use Flex API to detect partial refunds
IDs use Flex format (fprod_, fsub_, fcus_) instead of Stripe format (prod_, si_, cus_) — treat all IDs as opaque strings

These differences are inherent to the RevenueCat External Purchases API and have been confirmed with the RevenueCat team (March 2026). Revenue is always accurately tracked inside RevenueCat — these differences only affect webhook payload fields.

Subscription Lifecycle Events

Flex syncs the following RevenueCat event types. This is the complete list — every event type that Flex sends to RC:

Flex Internal Event	RC Webhook Event Type	Description	Includes Payment?
`TrialPurchase`	`INITIAL_PURCHASE`	Free trial started ($0 invoice). Subscription created with status: trialing.	No
`TrialConversion`	`INITIAL_PURCHASE`	Trial converted to paid subscription. First real payment processed.	Yes (positive amount)
`Renewal`	`RENEWAL`	Subscription renewed at start of a new billing period.	Yes (positive amount)
`BillingSucceeds`	`RENEWAL`	Payment recovered after a past_due period. Same logic as Renewal.	Yes (positive amount)
`BillingIssue`	`BILLING_ISSUE`	Payment failed during renewal. Subscription enters grace period.	No
`Expiration`	`EXPIRATION`	Subscription access ended. Triggered by Stripe `customer.subscription.deleted`.	No
`CancelAtPeriodEnd`	`CANCELLATION`	Subscription set to not renew at end of current period. Still active.	No
`UndoCancelAtPeriodEnd`	`UNCANCELLATION`	Cancel-at-period-end reversed. Subscription will renew again.	No
`Refund`	`CANCELLATION`	Refund issued. Sends expired status + negative payment to adjust revenue.	Yes (negative amount)

ProductChange (upgrades/downgrades) is not currently supported. All other subscription lifecycle events are fully implemented and synced in real-time.

Stripe Trigger Mapping

Each Flex RC sync event is triggered by a specific Stripe webhook event:

Stripe Webhook Event	Condition	Flex RC Event Type
`invoice.payment_succeeded`	`amount_paid == 0` AND `status == trialing`	`TrialPurchase`
`invoice.payment_succeeded`	`status == trialing` AND `amount > 0`	`TrialConversion`
`invoice.payment_succeeded`	`billing_reason == subscription_create`	`TrialConversion`
`invoice.payment_succeeded`	`status == active`, billing cycle	`Renewal`
`invoice.payment_succeeded`	`status == past_due`	`BillingSucceeds`
`invoice.payment_failed`	Any	`BillingIssue`
`customer.subscription.updated`	`cancel_at_period_end`: false → true	`CancelAtPeriodEnd`
`customer.subscription.updated`	`cancel_at_period_end`: true → false	`UndoCancelAtPeriodEnd`
`customer.subscription.deleted`	Any	`Expiration`
`charge.refund.updated`	`refund status == succeeded`	`Refund`

Event Sequences by Scenario

New Subscription (No Trial)

#	RC Event Type	cancel_reason	price	gives_access
1	`INITIAL_PURCHASE`	—	$179.99	true

New Subscription (With Free Trial)

#	RC Event Type	Trigger	price	status
1	`INITIAL_PURCHASE`	Trial starts ($0 invoice)	$0.00	trialing
2	`INITIAL_PURCHASE`	Trial converts (first payment)	$179.99	active

Both events appear as INITIAL_PURCHASE in RC webhooks. The first has price 0 and status trialing; the second has the actual price and status active.

Renewal

#	RC Event Type	price	gives_access
1	`RENEWAL`	$179.99	true

Payment Failure → Recovery

#	RC Event Type	Trigger	status	gives_access
1	`BILLING_ISSUE`	Payment fails	in_grace_period	true (grace period)
2	`RENEWAL`	Payment retried and succeeds	active	true

If payment never recovers, the subscription eventually receives an EXPIRATION event when Stripe deletes it.

Cancel at End of Billing Period (Option A)

#	RC Event Type	cancel_reason	gives_access	auto_renewal_status
1	`CANCELLATION`	`UNSUBSCRIBE`	true	will_not_renew

Subscription remains active until the current period ends. Access continues during this time.

Undo Cancel / Re-subscribe Before Period Ends

#	RC Event Type	gives_access	auto_renewal_status
1	`UNCANCELLATION`	true	will_renew

Cancel Immediately + Full Refund (Option B)

#	RC Event Type	cancel_reason / expiration_reason	price	gives_access
1	`CANCELLATION`	cancel_reason: `UNSUBSCRIBE`	$0.00	true
2	`EXPIRATION`	expiration_reason: null	$0.00	false
3	`CANCELLATION`	cancel_reason: `CUSTOMER_SUPPORT`	$0.00	false

Event #3 is the refund signal. In a native Stripe integration, price would be -

179.99. With the External API, the price is always `

0.00`. Revenue IS correctly adjusted inside RC — query the Subscriber API to confirm net revenue.

Cancel Immediately + Prorated Refund (Option C)

#	RC Event Type	cancel_reason / expiration_reason	price	gives_access
1	`EXPIRATION`	expiration_reason: null	$0.00	false
2	`CANCELLATION`	cancel_reason: `UNSUBSCRIBE`	$0.00	true

No CANCELLATION (CUSTOMER_SUPPORT) event is generated for prorated refunds. The refund is invisible in webhooks. Revenue is adjusted internally in RC. Use the Flex API or RC Subscriber API for refund details.

Subscription Expires Naturally (After Cancel at Period End)

#	RC Event Type	expiration_reason	gives_access
1	`EXPIRATION`	null	false

This fires when the billing period ends after a CancelAtPeriodEnd was set.

Field Reference

Every RC webhook event from Flex will have these field values:

Field	Value	Notes
`store`	`"EXTERNAL"`	Always EXTERNAL for Flex-managed subscriptions
`environment`	`"SANDBOX"` or `"PRODUCTION"`	Matches the Flex partner’s test_mode setting
`product_id`	`fprod_xxx`	Flex product ID (not a Stripe product ID)
`transaction_id`	`fsub_xxx`	Flex subscription ID
`original_transaction_id`	`fsub_xxx`	Same as transaction_id
`app_user_id`	`fcus_xxx`	Flex customer ID
`currency`	`USD`	ISO 4217 currency code
`price`	`0.0` or positive amount	Never negative — see Refund Handling
`price_in_purchased_currency`	Same as price	Always matches price
`commission_percentage`	`0.0`	Flex handles its own payment processing
`takehome_percentage`	`1.0`	Flex handles its own payment processing
`tax_percentage`	`0.0`	Tax reported as zero
`country_code`	`null`	Not available via External API
`entitlement_ids`	`null` or populated	Depends on RC project entitlement configuration
`renewal_number`	`1`	Always 1 — External API limitation
`is_family_share`	`false`	Not applicable
`period_type`	`"NORMAL"`	Always NORMAL
`subscriber_attributes`	`{}`	Empty unless custom attributes configured
`metadata`	`null`	Not populated
`expiration_reason`	`null`	Never populated for External store
`cancel_reason`	`"UNSUBSCRIBE"` or `"CUSTOMER_SUPPORT"`	UNSUBSCRIBE = user-initiated cancel. CUSTOMER_SUPPORT = refund.

Key Differences from Stripe-Native Integration

If your webhook consumer was originally built for a native Stripe → RevenueCat integration, the following differences apply when receiving events from Flex. These are inherent to the RevenueCat External Purchases API and have been confirmed with the RevenueCat team (March 2026).

Field	Stripe-Native Value	Flex External Value	Why	Impact
`store`	`"STRIPE"`	`"EXTERNAL"`	RC sets this based on app type	Must accept both values
`price` (refund)	Negative (e.g. `-179.99`)	Always `0.0`	External API does not expose payment amounts in webhook price field	Cannot detect refund amount from webhook
`price_in_purchased_currency` (refund)	Negative	Always `0.0`	Same as above	Same as above
`expiration_reason`	`"UNSUBSCRIBE"`	`null`	External API does not set this field	Accept null as valid
`commission_%`	~0.03 (Stripe fee)	`0.0`	Flex handles its own payment processing	Informational only
`takehome_%`	~0.97	`1.0`	Derived from zero commission	Informational only
`product_id`	`prod_xxx` (Stripe)	`fprod_xxx` (Flex)	Flex uses its own product IDs	Treat as opaque string
`transaction_id`	`si_xxx` (Stripe sub item)	`fsub_xxx` (Flex sub)	Flex uses its own subscription IDs	Treat as opaque string
`app_user_id`	`cus_xxx` (Stripe customer)	`fcus_xxx` (Flex customer)	Flex uses its own customer IDs	Treat as opaque string
`renewal_number`	Increments each period	Always `1`	External API does not track renewal count	Track externally if needed

These differences are not bugs. They are confirmed RevenueCat platform behavior for the External Purchases API. Flex sends all available data correctly; the External API simply exposes different fields than native integrations.

Refund Handling

Refund visibility in RC webhooks depends on the refund type and flow:

Scenario	RC Webhook Event	cancel_reason	price	Revenue Adjusted in RC?
Full refund (immediate cancel + refund)	`CANCELLATION`	`CUSTOMER_SUPPORT`	0.0 (not negative)	Yes — gross = $0.00
Prorated refund	No specific refund event	N/A	N/A	Yes — gross = net amount
Custom refund amount	No specific refund event	N/A	N/A	Yes — gross = net amount
Cancel at period end then later refund	May not generate `CUSTOMER_SUPPORT`	N/A	N/A	Yes — always adjusted

How to detect and measure refunds

Method	How	Detects Full Refunds?	Detects Prorated Refunds?	Gets Refund Amount?
RC Webhook	`cancel_reason == "CUSTOMER_SUPPORT"`	Yes (2-step flow only)	No	No (price is 0.0)
RC Subscriber API	`GET /v1/subscribers/{id}` → check `total_revenue_in_usd`	Yes	Yes	Yes (net revenue)
Flex API / Webhooks	Flex refund events with amounts, types, timestamps	Yes	Yes	Yes (exact amount)

Recommended: Use Flex webhooks for refund tracking (exact amounts and types) and RC webhooks for subscription lifecycle (active, canceled, expired, billing).

Recommendations for Webhook Consumers

Handling the store field

Accept events where store is either "STRIPE" or "EXTERNAL":

if event.store in ["STRIPE", "EXTERNAL"]:
    process_event(event)

Detecting subscription state changes

Use the event type and cancel_reason to determine subscription state:

Condition	Meaning
`type == INITIAL_PURCHASE`	New subscription or trial conversion
`type == RENEWAL`	Successful renewal payment or billing recovery
`type == CANCELLATION` AND `cancel_reason == UNSUBSCRIBE`	User canceled (won’t renew, still active)
`type == CANCELLATION` AND `cancel_reason == CUSTOMER_SUPPORT`	Refund issued (full refund only)
`type == UNCANCELLATION`	Cancel reversed, will renew again
`type == EXPIRATION`	Access revoked, subscription ended
`type == BILLING_ISSUE`	Payment failed, in grace period

Handling refunds

Detect refund occurrence

Check for cancel_reason == "CUSTOMER_SUPPORT" on CANCELLATION events.

Do NOT rely on negative price

The price will always be 0.0 for External store events.

Get refund amounts

Use the Flex API or RC Subscriber API for exact refund amounts.

Handle prorated/custom refunds

No RC webhook event is generated for these — use Flex webhooks instead.

Handling expiration events

Accept expiration_reason: null. The External store does not populate this field. To determine why a subscription expired, look at the preceding CANCELLATION event’s cancel_reason.

ID formats

Treat all IDs as opaque strings. Do not parse, validate format, or assume a prefix:

ID Field	Stripe-Native Format	Flex Format
`product_id`	`prod_xxx`	`fprod_xxx`
`transaction_id`	`si_xxx`	`fsub_xxx`
`original_transaction_id`	`si_xxx`	`fsub_xxx`
`app_user_id`	`cus_xxx`	`fcus_xxx`

Example Payloads

All payloads below are from real webhook captures in the RevenueCat sandbox.

{
  "api_version": "1.0",
  "event": {
    "type": "INITIAL_PURCHASE",
    "store": "EXTERNAL",
    "environment": "SANDBOX",
    "product_id": "fprod_xxx",
    "transaction_id": "fsub_xxx",
    "original_transaction_id": "fsub_xxx",
    "app_user_id": "fcus_xxx",
    "currency": "USD",
    "price": 0.0,
    "price_in_purchased_currency": 0.0,
    "period_type": "NORMAL",
    "renewal_number": 1,
    "is_family_share": false,
    "commission_percentage": 0.0,
    "takehome_percentage": 1.0,
    "tax_percentage": 0.0,
    "country_code": null,
    "entitlement_ids": null,
    "expiration_reason": null,
    "cancel_reason": null,
    "subscriber_attributes": {}
  }
}

{
  "api_version": "1.0",
  "event": {
    "type": "INITIAL_PURCHASE",
    "store": "EXTERNAL",
    "environment": "SANDBOX",
    "product_id": "fprod_xxx",
    "transaction_id": "fsub_xxx",
    "app_user_id": "fcus_xxx",
    "currency": "USD",
    "price": 179.99,
    "price_in_purchased_currency": 179.99,
    "commission_percentage": 0.0,
    "takehome_percentage": 1.0,
    "tax_percentage": 0.0,
    "renewal_number": 1
  }
}

{
  "api_version": "1.0",
  "event": {
    "type": "RENEWAL",
    "store": "EXTERNAL",
    "product_id": "fprod_xxx",
    "app_user_id": "fcus_xxx",
    "currency": "USD",
    "price": 179.99,
    "price_in_purchased_currency": 179.99,
    "commission_percentage": 0.0,
    "takehome_percentage": 1.0,
    "renewal_number": 1
  }
}

{
  "api_version": "1.0",
  "event": {
    "type": "CANCELLATION",
    "cancel_reason": "UNSUBSCRIBE",
    "store": "EXTERNAL",
    "product_id": "fprod_xxx",
    "app_user_id": "fcus_xxx",
    "currency": "USD",
    "price": 0.0,
    "price_in_purchased_currency": 0.0,
    "commission_percentage": 0.0,
    "takehome_percentage": 1.0
  }
}

{
  "api_version": "1.0",
  "event": {
    "type": "CANCELLATION",
    "cancel_reason": "CUSTOMER_SUPPORT",
    "store": "EXTERNAL",
    "product_id": "fprod_xxx",
    "app_user_id": "fcus_xxx",
    "currency": "USD",
    "price": 0.0,
    "price_in_purchased_currency": 0.0,
    "commission_percentage": 0.0,
    "takehome_percentage": 1.0
  }
}

Price is 0.0, not negative. Revenue is adjusted inside RC but not reflected in this webhook payload.

{
  "api_version": "1.0",
  "event": {
    "type": "UNCANCELLATION",
    "store": "EXTERNAL",
    "product_id": "fprod_xxx",
    "app_user_id": "fcus_xxx",
    "currency": "USD",
    "price": 0.0,
    "commission_percentage": 0.0,
    "takehome_percentage": 1.0
  }
}

{
  "api_version": "1.0",
  "event": {
    "type": "EXPIRATION",
    "expiration_reason": null,
    "store": "EXTERNAL",
    "product_id": "fprod_xxx",
    "app_user_id": "fcus_xxx",
    "currency": "USD",
    "price": 0.0,
    "price_in_purchased_currency": 0.0,
    "commission_percentage": 0.0,
    "takehome_percentage": 1.0
  }
}

{
  "api_version": "1.0",
  "event": {
    "type": "BILLING_ISSUE",
    "store": "EXTERNAL",
    "product_id": "fprod_xxx",
    "app_user_id": "fcus_xxx",
    "currency": "USD",
    "price": 0.0,
    "commission_percentage": 0.0,
    "takehome_percentage": 1.0
  }
}

FAQ

Why is store EXTERNAL instead of STRIPE?

Flex uses RevenueCat’s External Purchases API to sync subscription data. RC automatically sets store to "EXTERNAL" for all events processed through this API. This is expected behavior, not a misconfiguration.

Why is price 0.0 on refund events instead of negative?

The External Purchases API does not expose payment amounts in the webhook price field. Flex sends the correct negative payment to RC, and revenue IS adjusted correctly inside RC. But the webhook event’s price field is derived from the subscription record, not the payment. This is a confirmed RevenueCat platform limitation (verified March 2026).

How do I know the refund amount?

Three options:

RC Subscriber API: GET /v1/subscribers/{app_user_id} — check total_revenue_in_usd
Flex Webhooks: Use Flex’s own webhook events, which include exact refund amounts and types
Flex API: Query the Flex API for subscription/refund details

Why is there no refund event for prorated refunds?

RevenueCat only generates a CANCELLATION (CUSTOMER_SUPPORT) event for full refunds processed through the External API. Prorated and custom refunds adjust revenue internally but do not trigger a distinct webhook event. Use the Flex API or RC Subscriber API to detect partial refunds.

Why is expiration_reason null?

The External Purchases API does not have a mechanism to set the expiration reason. This field is only populated for native integrations (Apple, Google, Stripe). To determine why a subscription expired, check the cancel_reason on the preceding CANCELLATION event.

Is revenue correctly tracked despite these differences?

Yes. Revenue (including refund adjustments) is always accurate in RC. The differences are only in webhook event payloads, not in RC’s internal data. You can always query GET /v1/subscribers/{id} to get accurate revenue figures.

Does Flex support trial subscriptions?

Yes. Flex syncs both TrialPurchase (trial start, $0 invoice) and TrialConversion (first real payment after trial). Both appear as INITIAL_PURCHASE in RC webhooks — differentiate by checking price (0.0 for trial start, positive for conversion).

Does Flex support undo-cancel (re-subscribe)?

Does Flex handle billing failures and recovery?

Yes. BillingIssue is sent when payment fails (status: in_grace_period, gives_access: true). BillingSucceeds is sent when payment recovers (same logic as Renewal).

Will these differences change in the future?

These are inherent to the RevenueCat External Purchases API as of March 2026. If RC updates the External API to support additional fields, Flex will adopt them. This document will be updated accordingly.

Overview

Integration

Product and Prices

Subscriptions

Refunds

Disputes

Webhooks

Dashboard

Integrating Flex with RevenueCat

Overview

Installation Guide

How Flex Integrates with RevenueCat

Native Stripe Integration

Flex External Purchases API

Subscription Lifecycle Events

Stripe Trigger Mapping

Event Sequences by Scenario

Field Reference

Key Differences from Stripe-Native Integration

Refund Handling

How to detect and measure refunds

Recommendations for Webhook Consumers

Handling the store field

Detecting subscription state changes

Handling refunds

Handling expiration events

ID formats

Example Payloads

FAQ

Overview

Integration

Product and Prices

Subscriptions

Refunds

Disputes

Webhooks

Dashboard

​Overview

​Installation Guide

​How Flex Integrates with RevenueCat

Native Stripe Integration

Flex External Purchases API

​Subscription Lifecycle Events

​Stripe Trigger Mapping

​Event Sequences by Scenario

​Field Reference

​Key Differences from Stripe-Native Integration

​Refund Handling

​How to detect and measure refunds

​Recommendations for Webhook Consumers

​Handling the store field

​Detecting subscription state changes

​Handling refunds

​Handling expiration events

​ID formats

​Example Payloads

​FAQ

Overview

Installation Guide

How Flex Integrates with RevenueCat

Subscription Lifecycle Events

Stripe Trigger Mapping

Event Sequences by Scenario

Field Reference

Key Differences from Stripe-Native Integration

Refund Handling

How to detect and measure refunds

Recommendations for Webhook Consumers

Handling the store field

Detecting subscription state changes

Handling refunds

Handling expiration events

ID formats

Example Payloads

FAQ