Tenure of office of Auditor-General (National Assembly)
Section 87(1) · 1999 Constitution (2004 edition)
What Constitution says
(1) A person holding the office of the Auditor-General for the Federation shall be removed from office by the President acting on an address supported by two-thirds majority of the Senate praying that he be so removed for inability to discharge the functions of his- office (whether arising from infirmity of mind or body or any other cause) or for misconduct.
This is the 1999 Constitution as published in 2004. Later amendments aren't included yet, so a section may have changed since.
Original source
Official Gazette · CFRN 1999 official PDF · printed page 55. Original document
Release: draft-c8d50d87fae9. Source scope, review and corrections