Branch auditors to conduct the audit in same fashion as done for Head Office. Proper communication shud be there between branch and principal auditors.branch auditors to forward their reports to principal auditors.
Principal auditors will look at the organization as a whole and file ITR as one. Branch auditors need to only forward their reports to principal auditors. However if there are no branch auditors and principal auditors are the same for both branch and HO then principal auditors will only prepare audit reports for branch and HO and file the returns as one for entire organization