Once you have tested SSO login thoroughly,  you might want to force SSO login. 

To force SSO login, you need to make the following changes:

1. Enable the "Force SSO Login" option in the SAML Add-on settings:

2. Disable the so-called WebSudo feature in JIRA by specifying the following line in your jira-config.properties file:

jira.websudo.is.disabled = true

(info) You will need to restart your JIRA server for this setting to take effect.

For more details, please refer to Configuring secure administrator sessions.