A foreign company cannot do business in India without registering with the Registrar of Companies under the Companies Act, 2013. The foreign company must first obtain a certificate of incorporation from the Registrar and then comply with other legal requirements, such as obtaining PAN and TAN numbers and registering with the Service Tax department, if applicable. Foreign companies must also comply with the Foreign Exchange Management Act and the Indian Income Tax Act. Failing to comply with these requirements can result in significant penalties and legal consequences.