When should a company be formed? Technical criteria for the transition from natural person to legal person in Mexican MSMEs. By German A. Rivera Medina, Brian A., Para Ramirez, Eduardo L., Valdivia Mezcua, and Antonio Riestro Romero. Bachelor's Degree in Accounting and Corporate Governance, Itiso PAP Professor, Metro. Daniel Rubalcaba Benegas. Popular science article prepared for Ser Empresario magazine. Ciudad Juarez Chihuahua. Summary. This professional application project, PAP at ITISO, a training experience that addresses real-world problems, aims to establish clear criteria to guide micro, small, and medium-sized enterprises MSMEs in their decision to transition from sole proprietorships to corporations. Based on real-world cases handled by three accounting firms, AFV consultors, Goitorchua Bores y Asociados and J. Del Rio, and drawing on a review of the Mexican legal and tax framework, a recurring problem is identified. The lack of clear criteria for determining the optimal time to incorporate, which generates asset risks, tax inefficiencies, and limitations to growth. As a response, a comprehensive advisory tool is proposed that integrates financial, tax, and legal variables to contribute to informed and assertive decision-making. What is the PAP of accounting firms, a TISO? The Professional Application Project, PAP, at the accounting firm represents a comprehensive space where students not only reinforce and apply their theoretical knowledge of laws, codes, and tax planning in real-world scenarios, but also assume the social responsibility inherent in their future profession. It is noteworthy that the core of this project lies in its direct connection with the community through free consultations for anyone who needs them, as well as the development of professional internships in different accounting firms, each with its own unique work methods that contribute holistically to the project. In this way, students gain experience in the workplace and develop critical and ethical thinking, aligning themselves with the university's commitment to a solidarity economy that seeks to put accounting tools at the service of social well-being and dignified work through a research project such as the one described in this document. The context and the problem. In Mexico, more than 4.9 million economic units operate. Approximately 99.8% are MSMEs and generate around 70% of employment, Iniji 2020. Their greatest vulnerability is their low survival rate. Of every 100 businesses that are created, 31 close before the first year and another 21 before the second, Iniji 2024. Behind many of these figures lies a common cause, a lack of planning, which includes premature or late decisions on the legal structure. Most people start their businesses as sole proprietors because of its simplicity. As revenue, operations, and partners grow, the need for a more formal structure arises. The problem is that this transition is rarely planned. Incorporating prematurely burdens the business with costs it cannot yet sustain, while postponing it when required exposes personal assets, increases the tax burden, especially when exceeding resico thresholds, and closes access to financing, tenders, and contracts with large clients who require a legal entity as a counterparty. Evidence from practice. The research and data collection were conducted anonymously. The results focused on six cases handled in the offices where the project members were completing their professional internships. The sample size is small because the population is also small, as there are few individual taxpayers with the minimum requirements to transition to incorporation as legal entities. A pattern was observed. Insert image table 1. In four of the six cases, the lack of criteria resulted in unfavorable economic or patrimonial consequences. Only where there was prior comprehensive advice, cases C and E, was the result favorable. The proposal, a package of four complementary products, tools available to anyone, is proposed, covering the four dimensions of the decision. Interactive guide with decision tree, revenue, partners activity, financing, and exposure. Asset management When is it advisable to establish one? Comparative table of tax regimes, RESICO PF, Business Activities, RESICO PM, and General Regime of PM. With simulations for $1.50, $3.50 and $7 million. How much does it impact? A comparative table of types of companies, SAS, DARL, SAS Cooperative, among others, according to Capital, Partners, and Liability. Which structure to choose. Advisory protocol for law firms, with a checklist of procedures before the Ministry of Economy. Notary SAT IMSS Infinavit and where applicable, SDPS reps. How to execute the transition. Conclusion. Deciding when to incorporate is not a mere formality, but a strategic planning decision that impacts the continuity and growth of the business. The proposed tool translates a complex legal and tax framework into clear and actionable criteria, strengthening responsible formalization and strategic, ethical, and sustainable tax compliance. This fulfills the purpose of the PAP Professional Action Plan Learning to Transform Reality with an ethical commitment to the environment.