There is a database with physical and legal. persons. Addresses, phone numbers, personal data, email, and more. What methods can be used to determine what user is using multiple accounts for work and link them in the database?
In this situation, in my opinion, options 2. Or indirectly (to write the system of analysis all at once, Cookies, IP addresses, etc., which would have tied everything together and gave a certain percentage of probability that the user belongs to one group or another company) or You can ask the user which company they belong to.