Why does the completeness of sales have to be to be assessed as high risk? It completely depends on the company, its transactions and its internal control systems. In a cash business, completeness of sales will often be high risk because sales might not be rung up on the cash register and sales therefore not recorded. In a business making credit sales, completeness will usually be much less of a risk.
No areas ever have to be assessed as high risk: everything depends on the client.