I was able to replicate this same error and I was able to fix it by changing "sender_payout_header" to "sender_batch_header". This documentation says you must use "sender_payout_header", but I was never able to get it to work: https://developer.paypal.com/docs/payouts/integrate/api-integration/#2-create-payout This documentation shows that you should use "sender_batch_header" with everything else remaining the same and it seems to work: https://developer.paypal.com/docs/api/payments.payouts-batch/v1/ And the note you mentioned is PayPal's way to force errors. You can see others here: https://developer.paypal.com/docs/payouts/integrate/test-payouts/#test-values This seems to get checked first, which is why the post call still went through. Not a great workflow, but I wouldn't get too hung up on it.
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