The Plainspeak / Investing

Investing · 3 min

The power of step-up SIPs

The 10% raise you already get, turned into a second one for your future self. What 25 years of Sensex history shows.

By 37xBetter · Last reviewed September 2026

A flat SIP feels disciplined. It is also a shrinking SIP. Every year, inflation and your own rising lifestyle take a bite out of what that fixed debit really means, so a SIP that never moves sends a smaller slice of you forward each year. There are three ways to run one, and WhiteOak Capital ran all three on 25 years of actual BSE Sensex history. The result is striking, and the honest lesson inside it is more useful than "step-up equals magic".

Three ways to run a SIP

Normal. The same amount every month, a flat ₹10,000. Fixed top-up. Raise it by a fixed rupee amount each year, here +₹1,000 a month annually. Variable top-up. Raise it by a fixed percentage, a 10% step-up running ₹10,000, ₹11,000, ₹12,100, with the increase itself growing.

25 years of real Sensex history

What ₹10,000 a month became under each approach:

Source: WhiteOak Capital SIP study (BSE Sensex TRI), June 2026. Past returns, not a promise.

The honest part

Over those 25 years the return per rupee was almost identical, and the top-up was slightly lower: the normal SIP earned an XIRR of 13.7%, the fixed top-up 13.3%, the variable 12.9%. The variable plan made the most money with the lowest return per rupee. The bigger corpus came mostly from investing more, added later, and each late rupee compounds for fewer years. So the takeaway is not "top-up beats starting big". Start as high as you can now, because early rupees are the most powerful you will ever invest. Then top up, so your rising income keeps getting invested and never sits idle.

The gap is small early, huge late

The reward for topping up arrives late, which is exactly why most people quit before it does.

Which top-up, and can you keep it?

A percentage top-up usually fits salaried earners best: it tracks your appraisal, which also arrives as a percentage, and it compounds on itself. A fixed rupee top-up is steadier and kinder when income is lumpy. Either way, the best top-up is the one you never stop. A 15% step-up looks best on paper and almost no one holds it for 25 years, so pick a rate you can keep through a flat-income year, usually 10%, tied to your appraisal month. And if income ever drops, pause the top-up, never the SIP itself.