Following are the crucial documents required for Trademark Registration Online in India:

For Individual:
Any one of the following documents are required for individuals:

Copy of Aadhar CardCopy of Aadhar Card;
PAN Card for trademarkPAN Card;
Driving License (Permanent)Driving License (Permanent)
For StartupFor Startup: For Startup, one is required to provide the Certificate of Recognition issued by the DPIIT.
For Sole ProprietorshipFor Sole Proprietorship: GST Registration Certificate is required for Registration.
For Partnership Firm or LLPFor Partnership Firm or LLP:
If the Registration of Trademark is done by a Partnership Firm then they must provide the following documents:

Partnership DeedPartnership Deed (if any);
Udyam Aadhar Registration Certificate Udyam Aadhar Registration Certificate (it’s optional);
GST CertificateGST Certificate.
If the Registration of Trademark is done by an LLP then they must provide the following documents:

LLP Incorporation CertificateLLP Incorporation Certificate;
LLP DeedLLP Deed;
GST CertificateGST Certificate;
Udyam Aadhar Registration CertificateUdyam Aadhar Registration Certificate (optional).
For MSMEFor MSME: If the Registration is done by MSME then they should provide Udyam Aadhar Registration Certificate issued by MSME.
For Private Limited CompanyFor Private Limited Company: If the application for Trademark Registration is filed by a Private Limited Company, then they should provide the following documents along with the application:
Incorporation CertificateIncorporation Certificate;
Udyam Aadhar Registration CertificateUdyam Aadhar Registration Certificate (optional).
For HUF (Hindu Undivided Family):
PAN Card of HUFPAN Card of HUF;
Deed of the Constitution of HUFDeed of the Constitution of HUF.
For a Trust:
Trust DeedTrust Deed;
Registration CertificateRegistration Certificate;
PAN Card in the Trust NamePAN Card in the Trust Name.
For a Society:
If a Society is pursuing the Trademark Registration Process then it shall submit the Registration Certificate which is issued by the Registrar of Co-operative Societies If a Society is pursuing the Trademark Registration Process then it shall submit the Registration Certificate which is issued by the Registrar of Co-operative Societies.
Following are some common documents required for Trademark Registration Online in India:
User affidavitUser affidavit;
Graphical Representation of TrademarkGraphical Representation of Trademark;
Power of Authorization of an AgentPower of Authorization of an Agent.