A DSC can't be extended once it expires, so you issue a fresh certificate — but renewing online before expiry is quick, and you can usually reuse your existing USB token.
How renewal works
Start a new application and pick the same certificate type and validity.
Complete Aadhaar eKYC and the short video verification.
Pay securely — the same transparent pricing as a new certificate.
Download the renewed certificate, usually the same day, onto your token.
Re-register the new certificate on each portal (GST, Income Tax, MCA, DGFT…).
Tip: renew a few days before expiry so your filings are never interrupted. Consider a 3-year certificate to avoid yearly renewals.