Respond to the following regarding an auditor's responsibility with respect to internal control in the audit of a non-issuer's financial statements:

In your own words, describe the nature and purpose of internal controls and why, in theory, they are important in a GAAS audit.

What is the auditor's minimum responsibility with respect to a client's internal control under AU-C 315? Briefly describe the steps an auditor should take in executing and documenting that responsibility regarding a client's system of internal control.

AU-C 315 provides a model to depict what good a system of internal control looks like. Briefly describe the model and how it should be used by an auditor in meeting their responsibilities with respect to internal control.

Explain the concept of "key" or "relevant" controls and how an auditor will apply that concept in their GAAS audit. What must an auditor do with these controls and during what phase of the audit?