ELSS has the shortest lock-in among 80C investments. With a SIP, each instalment is locked in for three years from its own date. Returns are market-linked and not guaranteed. The tax deduction is not available under the new tax regime.
Finance glossary
What is Equity-linked savings scheme (ELSS)?
An equity mutual fund with a three-year lock-in that qualifies for the Section 80C tax deduction under the old regime.