Lean Payments has some specific errors 4XX, in addition to the ones described in General errors.

Status	Code	Description
AMOUNT_UNDER_MIN_VALUE	400	The amount specified for the payment intent is lower than the minimum amount allowed for the currency. Use a higher amount and try again. The minimum amount allowed for AED is 10 and for USD is 3.
INVALID_AMOUNT	400	The amount specified for the payment intent is incorrectly formatted. Make sure the amount is formatted correctly and has the appropriate number of decimals for the currency specified.
INVALID_IBAN	400	The IBAN specified for the Payment Destination is invalid. It may be incorrectly formatted or our system detected that the IBAN is invalid. You can check if an IBAN is valid using https://www.iban.com/iban-checker.
INVALID_NAME	400	The name specified for the Payment Destination is invalid. You must enter the full name of the person or entity. The name string must be at least two words.
UNKNOWN_PAYMENT_DESTINATION	404	The payment_destination specified in your request does not exist.
UNKNOWN_PAYMENT_INTENT	404	The payment_intent specified in your request does not exist.
UNKNOWN_PAYMENT_SOURCE	404	The payment_source specified in your request does not exist or, when applicable does not belong to the customer also specified in the query parameters.

Lean uses conventional HTTP response codes with requests to help you identify errors and how to rectify them. We also provide a status within the body of an error response to indicate how to resolve the error that has occurred. Please review the documentation on the specific API you want to use to see the structure of the error response.

Error Code	Explanation
AMOUNT_OVER_MAX_VALUE	The amount specified for the payment intent is greater than the maximum amount allowed for the currency. Use a lower amount and try again. The maximum amount allowed for AED is 1,000,000 and for USD is 270,000.
ANOTHER_PAYMENT_ALREADY_IN_PROGRESS	User is initiating another payment while an existing payment is already in progress. Suggests a duplication by the user. End users are messaged to wait 10 minutes before attempting the payment again.
EU_ACCOUNT_LOCKED	Your online account has been locked by your bank. This can be confirmed by trying to log in to your bank's mobile application or website which will also give you more details about how to unlock your account. Once your account is unlocked, you will be able to successfully connect.
LOGGED_IN_ELSEWHERE	The bank rejected the connection because you logged into your bank account on another device. Please try again without logging in to your online banking elsewhere.
BANK_ISSUE	Your bank is currently experiencing technical problems. Please try again later.
UNSEEN_BANK_ERROR	Your bank has reported an error, please try again later. If this error continues, please contact customer service.
BANK_MAINTENANCE	Your bank is currently undergoing technical maintenance and online services are unavailable. Please try again later.
LEAN_ERROR	Generic response for an unclassified error. This may be an error with Lean or the bank - This is unlikely to be resolved without reaching out to our support team with the trace_id for further details on the logs that led to the transaction failing.
EU_FUNCTIONALITY_RESTRICTED	Your bank has restricted functionality on your account. Please try to log in to your bank's online web portal to resolve any issues or requirements.
KNOWN_UNSUPPORTED_MFA_BEHAVIOUR	We are unable to process this request, please try again later. If you continue to see this error, please get in touch with customer support with the support code below.
KNOWN_TRAFFIC_OUTSIDE_ALLOWED_REGION	We were unable to process this request because you have not enabled this service on your account.
ENTITY_ALREADY_CONNECTED	We could not connect this account since you have already connected an account for this bank. Please choose a different bank to connect this with or delete your existing connection with this bank and try again.
BENEFICIARY_RECENTLY_REMOVED	The bank has indicated that you recently removed the beneficiary you are trying to authorise. Please try again in 72 hours.
BENEFICIARY_DUPLICATE_NICKNAME	A beneficiary with the nickname %s already exists in your bank account. Please go to your online banking website and delete the beneficiary with this nickname before trying again.
BENEFICIARY_NOT_FOUND	The recipient of this payment was removed as a beneficiary for your bank account. Please contact customer support to add the recipient as a beneficiary.
BENEFICIARY_COOL_DOWN_INCOMPLETE	You cannot send a payment to this recipient right now because your bank has not yet activated the beneficiary.
INACTIVE_PAYMENT_SOURCE	You have already connected this bank account but your payment method has been deactivated. Please contact customer support for assistance.
BENEFICIARY_DAILY_LIMIT_EXCEEDED	You cannot set up payments right now because you have exceeded your bank's limit of three new beneficiaries per day. Please try again tomorrow.
EXISTING_BENEFICIARY_INVALID	The beneficiary that exists in your bank account is not correctly set up. Please go to your bank’s website and edit the beneficiary to include all necessary details including the city and country of the beneficiary.
INSUFFICIENT_BALANCE	There is insufficient balance in your account to cover this payment and any associated fees. Please try with another account or after you've refunded your account.
EXCEEDS_DAILY_LIMIT	You have exceeded your bank's limit for the value of online transfers that can be made in one day. Please try to make this payment tomorrow before making other online transfers.
ACCOUNT_SETTINGS_LIMIT_EXCEEDED	Your bank has rejected this payment because it is not permitted by your account settings. Please ensure your account settings allows payments of this type and amount before trying again.
PAYMENT_BELOW_MIN_AMOUNT	This transaction cannot be processed by your bank as it is too small. Please try again with a larger amount.
PAYMENT_ABOVE_MAX_AMOUNT	This transaction cannot be processed by your bank as it is too large. Please try again with a smaller amount.
SERVICE_NOT_SUPPORTED	We were unable to set up or initiate payments because you have not enabled this service on your account. To enable this, login to your online banking portal or mobile application and enable this functionality before trying again.
ONLINE_TRANSFERS_DISABLED	Online transfers are disabled for your bank account. Please enable online transfers through your bank's website before trying again.
NO_VALID_PAYMENT_ACCOUNTS	We could not find any accounts that are eligible for payments.
CURRENCY_UNSUPPORTED	We cannot currently process payments in the chosen currency with your bank. Please try your payment in another currency or with another bank.
REPEATED_TRANSACTION	Your bank has rejected this payment because a similar payment was made in the last few minutes. If you intended to make this payment, please try again after an hour.
BANK_FLAGGED_DUPLICATE_TRANSACTION	Your bank does not permit more than one transaction of the same amount to the same recipient within a 5 minute period. Please try again with a different amount or after waiting 5 minutes.
USER_CANCELLED	You have cancelled or rejected this transfer with your bank so it could not be processed. Please try again.
SESSION_EXPIRED_ON_OTP	The payment was rejected by the bank because the connection timed out and expired. Please try again and make sure to submit any OTPs within 1 minute.
CURRENCY_UNSUPPORTED_BANK	The bank does not support transfers to this country in the chosen currency. Please try again with another currency.
DESTINATION_COUNTRY_UNSUPPORTED	We cannot currently process payments to the destination country for the chosen bank.
DISABLED_BY_LEAN	This functionality has been temporarily disabled for this bank. Please try again later.
DISABLED_BY_CLIENT	This application has temporarily disabled functionality for this bank. Please try again later.
COOLDOWN_PAYMENT_LIMIT_EXCEEDED	Your bank requires you to wait for 6 hours before you can make this payment since this the first time you are transferring money to this entity. Please try to make this payment after 6 hours. We're sorry for this inconvenience.
USER_SEGMENT_MAX_REACHED	The entered amount exceeds the maximum daily limit for transfers from your bank. Please wait one business day for your limit to reset, or try again with a smaller amount.
UNSUPPORTED_ACCOUNT_TYPE	The account you selected does not allow payments to be initiated. Please try again with another account.
MISSING_PAYMENT_AUTHORIZATION_PERMISSION	You don't have permissions to authorize payments. Please connect or use a different account with authorizer permissions.
MISSING_PERMISSION_OR_NO_PAYMENTS	There are either no payments to authorize or you don't have payment authorization permissions with your connected account.