How many days after leaving the company, the company will undertake social security.

Legal analysis: employees who have worked for less than one month in the month of resignation need to pay social security for that month. Moreover, individuals and units need to pay social security fees in accordance with the provisions of national documents, and there can be no illegal acts related to violating the social insurance law.

Legal basis: Article 58 of the Social Insurance Law of People's Republic of China (PRC) stipulates that the employer shall apply to the social insurance agency for social insurance registration for employees within 30 days from the date of employment. If the social insurance has not been registered, the social insurance agency shall verify the social insurance premium it should pay. Employees-free individual industrial and commercial households who voluntarily participate in social insurance, part-time employees who do not participate in social insurance in the employing unit and other flexible employees shall apply to the social insurance agency for social insurance registration. The state establishes a national unified personal social security number. Personal social security number is a citizen's identity number.