Documentation for JIRA 4.3. Documentation for other versions of JIRA is available too.

There are three ways to find you Support Entitlement Number (SEN):

If you're using GreenHopper, the GreenHopper license appears above the JIRA one. The JIRA 'license details' link is towards the bottom of the list on the left hand side.

Select Administration >> License Details. The SEN is shown:

Your Support Entitlement Number is available in http://my.atlassian.com:

Your Support Entitlement Number (SEN) appears on the third page of your Atlassian Invoice.

See Finding Your Support Entitlement Number in the support space for more general information about how Atlassian Support uses this number.