The correct answers are: Cost of sales; Directors' bonuses; Marketing.

Revenue has increased slightly, but this does not at first glance appear to be a problem, as this could easily be explained by an inflationary price rise for instance. The tax charge is significantly different from the prior year, but it is not a large balance compared to the others and also there might be a number of justifiable reasons why the tax charge would fluctuate year on year, so this would not be of immediate concern.

Cost of sales and the related gross margin is an area of concern as it has fallen significantly, which might indicate an error in inventory, another error of omission. Directors' bonuses are the same as in the prior year, but are risky by their nature as they related to directors. The marketing expense seems to have risen significantly and there is not a corresponding significant rise in sales. Although there may be suitable explanations for this rise, the auditors should investigate it, particularly as, at 1% of revenue, marketing is a material balance.