The core principles of financial internal control are explained here: accounting and financial operations can be separated and the main purpose is the handling of cash and the copy of the movement thereof can be done by different persons. Liability for the performance of the job must be evidently stated so that there may be no reason for doubt or confusion later.
Too much assurance should not be pinned in one entity or individual. Nearly all scam have been committed by trusted officials or staff members. It is interesting to keep record that frauds have occurred owing to their being trusted. Relation opinion relating to shift of an employee from one job to another must be the inflexible guiding rule. And it is an effective safeguard against collusion and is predictable as an important canon of sound business.
Mechanization of the work wherever practicable and feasible should be resorted to, mechanical devices such as recording time clocks, cash register, calculation machines should be known. A system of control accounts must elegantly be fitted in the book keeping structure.
The work should be so managed that work done by one employee must be properly checked by self independent employee. Such continuous & constant checking goods moral control and the errors and the scams cannot go undetected.