In the course of reviewing the process of information and document flow in the accounting process within the framework of interaction between customers of the transfer of accounting functions and budget accounting centers, methodological approaches to determining risks and control procedures are investigated. It is shown that the most risky areas are located in the places where documents and information are transferred between customers and the budget accounting center (hereinafter referred to as BAC). Measures for mutual control of interaction participants are proposed. When considering the specifics of interaction between accounting centers and customers, the need to consider internal control as a system common to the participants of the insourcing accounting function is justified. The main elements of such a system are two entities – the customer of the function and the budget accounting center, its divisions and employees. The methodological basis of the unified internal control system of two subjects of interaction (BAC and customers) is proposed. It is proposed to build, evaluate and develop such an internal control system using common internal control components set out in joint regulatory documents. To take into account mutual risks and control actions, it is proposed to use a single matrix of risks and control procedures. A step-by-step scheme of interaction between BAC and customers in terms of the direction of document movement has been developed.