Discover Payment Decline Code
Discover Decline Code 40: Requested Function Not Supported
Category Transaction RestrictionsRetry Guidance Conditional Decline (Editorial Classification)By Payment Defender Editorial TeamUpdated July 17, 2026Last reviewed July 17, 2026
What Discover Decline Code 40 Means
Discover decline code 40 (Requested Function Not Supported) indicates that the requested function or transaction type is not supported.
Where the Response May Come From
Code 40 means the specific function or service requested is not supported for this card or in this context. It reflects the transaction request and issuer capabilities, so the processor response is the reference.
Common Reasons for This Response
Common causes include an unsupported transaction type for the card, terminal, or account.
Should the Merchant Retry the Payment?
A retry helps only if the request is changed to a supported function; sending the same unsupported request again repeats code 40.
Recommended Merchant Action
Confirm which functions the card and your integration support, adjust the request accordingly, or ask the customer to use a different payment method.
What to Tell the Customer
Let the customer know the requested option is not available on that card and suggest another payment method.
How to Reduce Similar Payment Failures
Reviewing which requested functions trigger code 40 helps align your checkout options with what Discover cards actually support in each context.
Important Limitations
Decline-code meanings vary by processor, gateway, and payment environment, and issuers do not always disclose the specific reason behind a response. The retry classification on this page is Payment Defender editorial guidance, not an official network rule. Merchants should confirm handling with their processor or gateway.
Related Decline Codes
Sources and Review Information
Last reviewed July 17, 2026
Raw network-response codes are supplemental to the complete processor or gateway response. Meanings and recommended actions can vary by issuer, processor, gateway, card network, payment method, region, and merchant configuration.