The core trade-off
A SIP in mutual funds is fully flexible — you choose the fund, the amount, and can redeem anytime. The National Pension System (NPS) is a retirement-specific, market-linked account: you choose an asset allocation (equity/corporate debt/government securities), but the money is locked in until age 60, and at exit at least 40% of the corpus must be used to buy an annuity (a fixed monthly pension) — only the remainder can be taken as a lump sum.
That lock-in is a deliberate design choice, not just a downside — it prevents the corpus from being spent before retirement, something a flexible SIP can't enforce on its own.
The tax advantage NPS has that SIP doesn't
NPS contributions qualify for a deduction under Section 80CCD(1) (within the overall ₹1.5 lakh Section 80C limit, same as ELSS mutual funds, PPF, and other 80C options), plus an additional ₹50,000 deduction under Section 80CCD(1B) — over and above the ₹1.5 lakh limit. A regular SIP in a non-ELSS equity fund gets no upfront deduction at all; even ELSS SIPs only count within the shared ₹1.5 lakh 80C limit, not an extra bucket.
For someone in the 30% tax bracket who has already used up their ₹1.5 lakh Section 80C limit elsewhere, contributing the full ₹50,000 to NPS saves roughly ₹15,600 in tax that year (30% plus 4% cess) — money a plain SIP contribution of the same amount wouldn't save.
This extra deduction is available only under the old tax regime — if you've opted for the new regime, this specific benefit doesn't apply, and the comparison tilts more toward SIP's flexibility.
What happens at retirement
At NPS exit, at least 40% of your corpus buys an annuity — a fixed monthly pension for life, but at annuity rates that are typically much lower than what a well-run mutual fund portfolio has historically returned over decades. The remaining up to 60% can be withdrawn as a tax-free lump sum. A SIP has no such requirement — you keep 100% control of how and when to draw down the corpus, but also no built-in provision to protect against outliving your savings.
A practical way to decide
If you haven't fully used your ₹1.5 lakh Section 80C limit, an ELSS SIP or PPF may make more sense first, since NPS's extra ₹50,000 benefit only matters once that base limit is already full. If it is full and you're in the old tax regime, adding ₹50,000/year to NPS is close to "free" tax savings that a plain SIP can't match rupee-for-rupee. Beyond that ₹50,000, most people prefer SIPs for further retirement savings — full flexibility and no forced annuity purchase, at the cost of losing NPS's specific extra deduction.