What does an insufficient funds error mean?

Has a customer shown you they have money in their account, but you're still getting an insufficient-funds error?

The only way to know for sure is for the cardholder to contact their bank about that specific charge. Banks make funds available differently — the money may have been pending rather than available when the charge ran. Stripe and the app only see the decline code the bank returns; the bank has the real reason.

For everyday declines in general, passing along more card details can help — the more a bank has to verify against, the more likely a charge goes through. When you can, collect the cardholder's name and ZIP code along with the card number.