A Cleaning audit is just a simple list the areas which you and the customer have aggreed at commencement of contract. Then make up a grading system for each of these areas eg: Very good, Good, Poor, Unsuitable. Build a blank form with all of this on it and fill the form in at regular intervals, sign it and get customer to sign it also. any areas which are below very good should be improved for the next audit.
Regards,
Alan Sharp
Cleaning Manager - Amazon.co.uk - Gourock