When a customized set of procedures are most effective for the clients needs.

When an opinion must be rendered on the potential for material misstatement in the financial statements and/or the effectiveness of internal control.  Typically required due to funding source or regulatory requirements; however any organization may need an audit if required in the board policies and procedures.

When you need a set of financial statements generated without assurance, with or without footnotes.

When you need limited assurance, without an opinion, with or without footnotes.