Chapter 24, Audit Documentation and Quality Control.

An auditor is appointed for only one year and must be formally reappointed (at the Annual General Meeting). Although there is no requirement to reissue a new engagement letter every year (it may include a sentence such as “This letter will be effective for future years unless it is terminated, amended or superseded” there are many reasons why the letter may be reissued.

“Recurring Audits
10. On recurring audits, the auditor should consider whether circumstances
require the terms of the engagement to be revised and whether there is a
need to remind the client of the existing terms of the engagement.
11. The auditor may decide not to send a new engagement letter each period.
However, the following factors may make it appropriate to send a new letter:
• Any indication that the client misunderstands the objective and scope of
the audit.
• Any revised or special terms of the engagement.
• A recent change of senior management or those charged with governance.
• A significant change in ownership.
• A significant change in nature or size of the client’s business.
• Legal or regulatory requirements.”