Stripe API errorNo such customer: ‘cus_…’; a similar object exists in test mode, but a live mode key was used to make this request

The usual causes, and the fix

1. 01

   Test IDs saved in your database

   During testing your app saved cus_ IDs on user records. After the switch to live keys, those IDs don’t exist. Save the mode next to each ID; when it doesn’t match the key in use, create a new customer instead of reusing the old ID. The same goes for saved price, product and subscription IDs.

   const customer = await stripe.customers.create({ email: user.email });
   await saveUser(user.id, {
     stripeCustomerId: customer.id,
     stripeLivemode: customer.livemode, // true for live keys
   });

2. 02

   Keys from different modes

   One environment variable still holds a test key while another holds a live one: the server on sk_test_ and the browser on pk_live_, or a preview deploy and production sharing a database. Test keys start with sk_test_ and pk_test_, live keys with sk_live_ and pk_live_; restricted keys use rk_test_ and rk_live_. Stripe now calls the test side a sandbox, and its keys still start with test. Check each environment.

3. 03

   The customer lives on a connected account

   With Stripe Connect, a customer created on a connected account only exists there. Requests about it need the Stripe-Account header with that account’s acct_ ID, or Stripe looks for it on your platform account and finds nothing.

   await stripe.customers.retrieve(customerId, {
     stripeAccount: connectedAccountId,
   });

4. 04

   A different account, sandbox or a deleted customer

   Each Stripe account and each sandbox has its own keys and its own data. If the message doesn’t mention the other mode, check that the key comes from the account that created the customer, and that nobody deleted it in the Dashboard.

Checked against the vendor’s docs on October 31, 2026: Stripe docs: API keys (sandbox versus live mode); Stripe docs: Error codes (resource_missing); Stripe docs: Make API calls for connected accounts.

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