Final answer:
If a client omits necessary information from financial statements, the auditor should include this information in their report if possible and express either a Qualified opinion or an Adverse opinion.
Step-by-step explanation:
When the client fails to provide necessary information for a fair presentation of financial statements, and if it is practicable, the auditor should include this information in their report. The auditor would then express either a Qualified opinion or an Adverse opinion. A Qualified opinion is given when there are material misstatements in the financial statements but they do not misrepresent the financial position of the company as a whole. An Adverse opinion is provided when the financial statements are materially misstated and do present a misleading view of the company's financial position.
In circumstances where it is not practicable for the auditor to present the missing information or when there is insufficient evidence to form an opinion, the auditor may issue a Disclaimer of opinion. This indicates that the auditor cannot express an opinion on the fairness of the financial statements, which is distinct from both qualified and adverse opinions.