Response from the Tax Agency:Return code 99

The error occurs when making payments or consultations in the Tax Agency payment gateway.The error is normally due to the use of an incorrect signature because it is either invalid due to the signature window not loading correctly or because you are using a DNIe and do not correctly select the authentication certificate or signature.

Error 99

Check that your electronic certificate is correctly installed and is valid.

In Internet Explorer, go to "Tools" (or the cogwheel icon located in the upper right corner of your browser) then "Internet Options".Select the "Contents" tab and click on "Certificates".The certificate should appear in the “Personal” tab.Check the expiry date.
In Microsoft Edge, go to the browser menu (three horizontal dots icon in the top right corner of the window), select "Settings", "Privacy, search and services". Find "Security” and click on "Manage certificates".The certificate must appear on the "Personal" tab for the installation to be valid.Check the "Expiry date" column.
In Google Chrome, go to the browser menu (icon with three points in the top right corner of the window), select "Configuration", "Privacy and security", "Security", "Advanced", "Manage certificates".The certificate must appear on the "Personal" tab for the installation to be valid.Check the "Expiry date" column.
In Mozilla Firefox, go to the "Tools" menu or click on the three horizontal lines icon at the top right of the browser.Then go to "Settings", "Privacy and security", "Security"In the "Certificates" section, click on "View certificates” and in the "Your certificates" section, check that your personal certificate is installed and is valid.
In Safari or Google Chrome on Mac, you must ensure that the electronic certificate is installed in the Keychain Access.To check the installed certificates, start the system application "Keychain Access" from "Finder", "Applications", "Utilities".Go to "Login", "My certificates" and check if your personal certificate appears in this storage.

If the certificates is issued by the FNMT or is an electronic DNI, you can check its validity from the CERES (Spanish Certification) website.If the certificate is correct, you will see a message reading “Your certificate has just been verified.Your FNMT digital certificate is valid and has not been revoked. Your certificate is working properly".

Verify status

If the certificate is issued by an entity other than FNMT or electronic DNI, you can validate it on the REDSARA system.

If you have several certificates installed in your browser, also check that you identify yourself at all times with the correct certificate and that the certificate is issued by one of the issuing entities authorised by the AEAT.

It is possible that, by using card certificates (e.g. DNIe) you select an invalid certificate to perform the electronic signature.The electronic ID has two certificates:the "Authentication" certificate and the "Signature" certificate.

Deactivate pop-up blocker on the browser.There may be a pop-up window that you have to accept and the blocker prevents it.Once the procedure has concluded, activate this option again:

In Internet Explorer, go to "Tools", "Internet options", "Privacy" and uncheck "Enable popup blocker".
In Microsoft Edge, go to "Settings and more" (three horizontal dots icon), "Settings", "Cookies and site permissions", "Pop-ups and redirects" and set it up so that pop-ups from the Tax Agency's website are allowed, using the "Add" button in the "Allow" section.
In Google Chrome, open the menu (three vertical dots icon), go to "Settings", "Privacy and security", "Site settings", "Content", "Pop-ups and redirects" and make sure that "Sites can send pop-ups and use redirects" is ticked.
In Mozilla Firefox, go to "Tools", "Options", "Privacy and security", "Permissions" and deselect "Block pop-up windows".
In Safari, go to "Preferences", "Security", "Web content" and uncheck "Block pop-up windows".If it is version 12, go to "Preferences", "Websites", tick "Pop-up windows" and disable website blocking for the AEAT website.

If the certificate is issued by an entity other than FNMT or electronic DNI, you can validate it on the REDSARA system.

Also check that you identify yourself at all times with the correct certificate if you have many installed in the browser, and that the certificate is issued by one of the issuing entities authorised by the Tax Agency.