Since the receiving function is largely clerical in nature, it is a misallocation of human resource to have managers perform clerical functions. Even though a manager can do a clerk's job, the reverse is usually not true. I strongly advise you to consider another employee for the receiving job.
In order for this to work, you may need to schedule receiving hours with your purveyors. And, you will also need to inform the receiving clerk job what was ordered, from whom, at what price and specification. This can be easily accomplished with purchase orders and specification training.
The person ordering the goods should be responsible for the completion of the purchase order. It takes little or no additional time for that person to write down what is being ordered if this is done while the order is being phoned in to the purveyor.
The fact is that receiving is vitally important and needs as much attention in the food-service industry and it gets in every other industry. Receiving must be done religiously, consistently and accurately. The end result will be well worth the effort. It is possible to absolutely eliminate the possibility of purveyor theft or invoice errors overnight. The effect of good receiving practices on profitability will be immediately evident.
Bill Schwartz is the President of System Concepts, Inc., the maker of FOOD-TRAK - Food and Beverage Management Software - http://www.foodtrak.com