When a step-up SIP is too aggressive for take-home
The first instalment of a step-up SIP is the easy number. The last instalment is the one that bounces. A 20% step looks generous on a corpus chart and impossible next to a take-home that does not rise by 20% every year. The 12% return below is an assumption. A 40% share of take-home is a planning habit on this site, not a Reserve Bank cap.
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Last monthly instalment, from a ₹15,000 start
Bar chart of a 5% step ending near ₹29,699 a month, an ₹80,000 take-home, and a 20% step ending near ₹1,92,588 a month.
- 5% step, year 15₹29,699
- Take-home in the example₹80,000
- 20% step, year 15₹1,92,588
Year one hides the problem
₹15,000 out of an ₹80,000 take-home is 18.75% of that month. It fits. The step-up SIP calculator then multiplies by 1.20 at each anniversary. After 14 raises the instalment is ₹15,000 × 1.20^14, about ₹1,92,588. That is the debit in year 15. The expected value at an assumed 12%, about ₹2.47 crore, is what you see if every one of those debits clears.
The same start with a 5% step finishes near ₹97,96,128 and asks for about ₹29,699 in the last year. You invest about ₹38,84,141 instead of about ₹1,29,66,319. The smaller corpus is the one that still resembles a salary. The larger one assumes the salary kept up with a 20% debit.
Take-home has to be a number you can defend
If you believe pay will rise 20% a year for 15 years, say so, and still leave room for rent, tax and a dull year. This sketch holds take-home at ₹80,000 on purpose, so the last instalment is compared with pay as it is, not with pay as the step hopes. A step that only works when income matches it is not a step you have funded.
There is no statutory share of salary that a SIP may use. The habit on this site is to keep loan EMIs in a band you can still pay, often talked about near 40% of take-home, and that band is not a law and not a SIP rule. A SIP of ₹1,92,588 against ₹80,000 fails the band and the bank mandate together.
- Year-one debit: ₹15,000, about 19% of an ₹80,000 take-home.
- 20% step, year 15: about ₹1,92,588 a month.
- 5% step, year 15: about ₹29,699 a month.
Read the last row before the corpus
The calculator's table has a monthly SIP column. Scroll to the last year before you look at the expected value. If that rupee figure is not plausible, lower the step and let the corpus fall. The 20% path invests about ₹1.30 crore. That cash has to come from somewhere. The chart is not creating it.
A one-time hike belongs in the flat amount, not in a permanent 20% step. Raise ₹15,000 to the new number you can pay every month, set the step back to something you have seen in dull years, and run it again.
The return does not rescue the mandate
Twelve percent changes the ending value. It does not pay the instalment. A higher assumed return makes an aggressive step look wiser and does nothing for the month the debit bounces. Keep the return dull enough that you still want the plan when the last instalment is the number you are judging.
If the 5% path's ₹97,96,128 is short of a goal, the fix is a longer tenure, a higher start you can pay now, or a smaller goal. It is not a 20% step you already know the salary will not match.
Worked example: 20% step against an ₹80,000 take-home
Both paths start at ₹15,000 and run 15 years at an assumed 12%. The take-home is held at ₹80,000 so the last debit has something real to sit beside.
| Item | Figure |
|---|---|
| Take-home in the example | ₹80,000 a month, not grown |
| Starting SIP | ₹15,000, about 19% of that take-home |
| 20% step, last instalment | About ₹1,92,588 |
| 20% step, expected value | About ₹2,47,11,605, from about ₹1.30 crore paid in |
| 5% step, last instalment | About ₹29,699 |
| 5% step, expected value | About ₹97,96,128, from about ₹38.84 lakh paid in |
Enter ₹15,000, a 20% step, 12% and 15 years, and read the final monthly SIP. If it is larger than a take-home you can explain, the corpus on that row is not your plan. Drop the step to 5% and read the last instalment again.
Sources
Results from FinanceChacha are estimates for planning, not financial or tax advice. Read the disclaimer.
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Open the calculator this guide refers to and run your own numbers.