Digital signature in GST registration allows e-sign via Aadhaar or DSC; companies and LLPs must use DSC. Digital signature options for GSTN registration permit taxpayers to sign electronically by e-signature linked to Aadhaar or by registering a Digital Signature Certificate (DSC) with the GST portal; companies and limited liability partnerships must use DSCs, and only Level 2 and Level 3 DSC certificates are acceptable.