"EA" is an "Enrolled Agent". Directly from the IRS webpage:
An enrolled agent is a person who has earned the privilege of
representing taxpayers before the Internal Revenue Service by either
passing a three-part comprehensive IRS test covering individual and
business tax returns, or through experience as a former IRS employee.
Enrolled agent status is the highest credential the IRS awards.
Individuals who obtain this elite status must adhere to ethical
standards and complete 72 hours of continuing education courses every
three years.
Enrolled agents, like attorneys and certified public accountants (CPAs),
have unlimited practice rights. This means they are unrestricted as to
which taxpayers they can represent, what types of tax matters they can
handle, and which IRS offices they can represent clients before. Learn
more about enrolled agents in
Treasury Department Circular 230
(PDF).
https://www.irs.gov/tax-professionals/enrolled-agents/enrolled-agent-information
