The 10-Year SIP Delay That Changed Two Retirement Stories

Ten years may not feel particularly significant when retirement is still decades away. In a long-term investment plan, however, those years can have an outsized effect on the eventual corpus. 

ET Money illustrates this through two hypothetical investors who follow almost identical investment plans but begin at different ages. 

Both invest through a monthly Systematic Investment Plan, or SIP. Both use the same assumed annual return of 12%, and both remain invested until the age of 60. 

The difference is straightforward: one begins at 25, while the other waits until 35. 

That 10-year gap produces very different outcomes. 

Starting at 25 versus starting at 35

In ET Money’s illustration, Aarav begins investing ₹5,000 every month at the age of 25 and continues until he turns 60. 

That gives him an investment period of 35 years. 

Over those years, his total contributions amount to ₹21 lakh. Assuming an annual return of 12%, the SIP calculator estimates his corpus at age 60 at approximately ₹2.76 crore. 

His estimated gains over the period amount to ₹2.55 crore. 

Karan follows the same ₹5,000 monthly SIP but begins at 35. 

He therefore invests for 25 years instead of 35. 

His total contribution by age 60 comes to ₹15 lakh. At the same assumed annual return of 12%, his estimated corpus reaches ₹85.11 lakh, including gains of ₹70.11 lakh. 

The difference in the amount actually contributed by the two investors is only ₹6 lakh. 

The difference in their estimated final corpus, however, is more than ₹1.9 crore. 

Why 10 additional years make such a large difference

The numbers demonstrate the effect of compounding over long periods. 

Starting earlier does more than add the contributions made during the first 10 years. It also gives those early investments considerably more time to potentially earn returns, and those returns more time to generate further returns. 

For Aarav, money invested at 25 can potentially remain invested for 35 years. 

Karan’s earliest contribution, made at 35, has only 25 years before the assumed retirement age. 

That additional decade explains why a relatively modest difference in total contributions can produce a much larger difference in the illustrated final corpus. 

It is important, however, to recognise what the calculation assumes. 

The 12% annual return used by ET Money is an illustration. Actual equity mutual fund returns can vary substantially over time and are not guaranteed.

Can doubling the SIP make up for starting late?

ET Money also examines another common assumption: if someone starts investing late, can they simply contribute more every month and catch up? 

In the second calculation, Aarav’s investment remains unchanged. 

He invests ₹5,000 a month from age 25 until 60, contributing ₹21 lakh in total and reaching the same estimated corpus of ₹2.76 crore under the 12% return assumption. 

Karan now doubles his monthly SIP. 

Instead of ₹5,000, he invests ₹10,000 every month from age 35 until 60. 

His total contributions rise to ₹30 lakh — ₹9 lakh more than Aarav invests over his lifetime. 

Yet his estimated corpus at 60 reaches approximately ₹1.70 crore. 

Despite investing twice as much every month and contributing more money overall, Karan still finishes more than ₹1 crore behind the estimated corpus of the investor who began 10 years earlier. 

The comparison highlights how difficult it can become to replace lost compounding time purely by increasing the monthly contribution later.

Starting late does not make the goal impossible

The calculation does not suggest that someone who has delayed investing cannot build a sizeable corpus. 

It means the required contribution becomes substantially larger when the investment period becomes shorter. 

ET Money estimates that Karan would need to invest roughly ₹15,000 every month from age 35 to reach approximately the same corpus that Aarav builds by investing ₹5,000 a month from age 25. 

In other words, a 10-year delay increases the required monthly SIP from around ₹5,000 to roughly three times that amount under the assumptions used in the illustration. 

That is a significant difference for household cash flow. 

An investor starting later may therefore have to compensate through some combination of higher contributions, a different target corpus or a longer investment period.

The contribution amount tells only part of the story

The comparison also shows why looking only at the amount invested can be misleading. 

Aarav contributes ₹21 lakh over 35 years. 

When Karan doubles his SIP to ₹10,000, he contributes ₹30 lakh over 25 years. 

On contributions alone, Karan has put considerably more money into the investment. 

Yet the calculator produces a smaller final corpus because his money has had less time to compound. 

The relationship between investment amount and investment time is therefore not linear. 

An additional rupee invested early has more potential compounding periods ahead of it than the same rupee invested much later.

A SIP does not guarantee a 12% return

The numerical difference in ET Money’s example depends heavily on the assumed return. 

A 12% annual return is used consistently across the scenarios to illustrate the effect of starting at different ages. It should not be read as a return that an equity mutual fund will necessarily generate. 

Actual returns can be higher or lower and can vary considerably from year to year. 

The final corpus would also change if the investor alters the SIP amount, pauses contributions, withdraws money, changes the investment period or earns a different return. 

The calculator therefore demonstrates a mathematical relationship rather than forecasting what an individual investor will receive at retirement. 

Time becomes harder to replace as the starting age rises

The central difference between the two hypothetical investors is not the investment product or assumed return. 

It is time. 

At ₹5,000 a month, the investor beginning at 25 contributes only ₹6 lakh more than the investor beginning at 35. Yet the estimated corpus at retirement is more than three times as large — ₹2.76 crore compared with ₹85.11 lakh. 

Even doubling the later investor’s SIP to ₹10,000 does not close the gap. 

Under the same assumptions, approximately ₹15,000 a month would be required from age 35 to reach a corpus similar to the one produced by a ₹5,000 monthly SIP started at 25. 

These figures are hypothetical, but the mathematical point behind them is straightforward. 

The longer an investment remains invested, the more time compounding has to work. When that time is lost, catching up generally requires substantially higher contributions. 

For retirement planning, the amount invested matters. But the ET Money illustration shows why the date on which those investments begin can matter just as much — and sometimes considerably more.