Automatic reading system, we propose to pre-classify the business documents by introducing an Automatic Recognition of Documents stage (ARD) as a preprocessing step. This important step will guide the other stages involved in the recognition process of the documents contents. Once the document class identified, the reading system will use correct information from the ARD stage to improve the segmentation of the layout, the recognition of the document structure, the parameterization of the OCR, and the final decision for the rejection. We propose in this paper an original method for the classification of business documents suited for complex layouts having great variability. We introduce the graph coloring approach for both layout analysis and documents classification. The proposed method is reliable, robust to various constraints and guarantees a real-time answer to the sorting of business documents.