Auditing has a very important place in today’s economic and financial world. The profession enables the proof checking of financial statements which gives peace of mind to those who read them. The profession is governed by the rules of ISA which encompasses all auditing work and also sets a standard, but still leaves a margin of breathing room to allow auditors to adapt to the ever changing rules of the environment of business and also to the rules of their clients. The objective of this summary is to present in a first section characterized by a normative rational vision how auditors determine which methodology they will be using in terms of the ISA norms and also the rules of the BDO manual of auditing. In the second part, this will be characterized by a strategic rational vision; this summary will discuss what tools and methods are used by auditors which allows said auditor to adapt in the best possible manner to the rules set by their clients. This summary to conclude will also present examples of work that has been accomplished in terms of the two previously stated categories by utilizing paperwork that in the BDO office. The combination of all these parts will show the essential notion of the risk of facing an audit. This notion is the most important when determining the methodology of the audit and also what work will ensue. We will retain in this summary that the auditor is able to adapt to the environment regardless of the lack of real time updating of the rules which only change when important events happen, even most likely the real world has already changed again since then and are thus not an adequate representation of the economic and financial reality