I agree with Amit. The report should preferably be in power point format but if your agreement with client is for a different format then follow the said agreed format.
Please spend initial slides/ pages on introduction/ scope coverage, disclaimers (exclusions, etc), then give synopsis (executive summary) of your observations. you may also want to give extent of cheking in the area covered in a separate slide.
Grade all observations in High, Medium and Low risk categories and arrange sequence of observations as High first, then medium and lastly, low risk observations. Always discuss your observations with process owners first before including in draft report. Include only those observations which cannot be resolved even after discussing with process owners.
Issue draft report for management comments. Obtain management comments which should include course of action to close the observations with due dates. Discuss with management if any of the comments/ course of action/ due dates is not acceptable so as to obtain revised comments.
Incorporate the management comments in the report and release the final report. As regards Annexures, you can copy them in MS excel format which can be pasted in power point file. Do add slide for list of addressees in the beginning whom report is being issued.