Response from the Financial Entity: Error 99
The "[code 99] Technical error" is a response from the collaborating entity that may occur when trying to make a payment, or a query thereof, on the AEAT payment gateway. This error prevents the operation from being carried out and, therefore, NRC is not generated as proof of payment.
The server of the bank with which you are carrying out the procedure may have technical problems. You should contact the bank for further information.
Alternatively, you can try to make payment later (perhaps it is just a server error) or indicate an account with a different bank, of which you are also the account holder.
Take into account that the Tax Agency is not responsible of the lack of response by the Collaborating Organisation and will not take any responsibility in the admission of order of charge. However, the account debit request forms digitally signed with the electronic certificates will be kept by the AEAT in a secure and complete manner.