The SIP date barely affects returns: in Nifty 50 data from October 2006 to September 2026, ₹10,000 a month ended between ₹81.64 lakh and ₹81.93 lakh whichever date from the 1st to the 28th it went in on, a gap under 0.4%. What costs money is a debit that fails, so the date that matters is one your account can always pay: for most salaried people, a few days after salary.

How much does the date change a 20-year SIP?

The figures use daily closes of the Nifty 50 Total Return Index (dividends reinvested), published by NSE Indices. Each ₹10,000 instalment buys at the close of the first trading day on or after the SIP date, and everything is valued at the close on 30 September 2026. A fund tracking the index would show slightly less after costs, by about the same on every date.

SIP date 20 years, Oct 2006 to Sep 2026 (₹24 lakh in) 10 years, Oct 2016 to Sep 2026 (₹12 lakh in)
1st ₹81.90 lakh ₹20.37 lakh
5th ₹81.84 lakh ₹20.33 lakh
10th ₹81.91 lakh ₹20.28 lakh
15th ₹81.77 lakh ₹20.30 lakh
20th ₹81.78 lakh ₹20.30 lakh
25th ₹81.82 lakh ₹20.29 lakh
28th ₹81.68 lakh ₹20.25 lakh

Over 20 years the yearly return (XIRR) ran from 11.02% to 11.08%. Across the 207 ten-year periods starting each month from August 1999 to October 2016, the gap between the best and the worst date was 0.17 percentage points a year at the median and 0.44 at the widest. No date is reliably the best date for a SIP: by XIRR, which allows for money on the 1st being invested about three weeks longer, a date from the 22nd to the 26th came out on top in 193 of those periods. In rupees, the 1st ended highest most often, in 81. Both edges are tiny, a pattern in past prices rather than a rule.

What did two bounced SIPs cost Tarun?

Tarun earns ₹24 lakh CTC, about ₹1,51,600 a month in hand under the new regime with PF on full wages (the CTC to in-hand table shows how), paid on the last working day. He runs four SIPs totalling ₹60,000: ₹20,000 on the 1st, ₹15,000 on the 5th, ₹15,000 on the 25th and ₹10,000 on the 28th. The last two usually fall before salary, and this year each bounced once.

SIP bounce charges come from the bank, not the fund: each bank sets its own fee for a returned auto-debit, about ₹250 to ₹500 a time in 2026 schedules of charges, and up to ₹550 for a second return in the same month at some banks, plus 18% GST. At ₹500 a time, Tarun's two bounces cost ₹1,180. The larger cost is the growth on units never bought, if that month's money is not invested later. In the 20-year data, a ₹15,000 instalment on the 25th gained ₹36,136 on average by 30 September 2026, and the October 2006 one gained ₹1,02,258.

On the same data, the move below, to the 3rd, 4th and 5th, ends ₹17,039 lower over 20 years, on about ₹4.91 crore, and ₹13,109 higher over 10. A missed instalment that is never made up, early in a long SIP, cost more than the whole 20-year date choice, which could have gone either way; investing the month's amount by hand the week it bounces leaves only the fee. Three bounces in a row on the same SIP would also end it: since 1 April 2024 a monthly SIP is cancelled after three failed debits in a row, and a quarterly one after two.

Which auto debit date suits a salary paid on the last working day?

When a month ends on a weekend or holiday, the last working day can be the 26th or earlier. A SIP on the 28th therefore lands after salary in some months and before it in others, and the 25th is before salary in almost every month, paid from whatever last month's pay has left; both bounced only when that balance ran short.

Tarun moves the 1st to the 3rd, the 25th to the 4th and the 28th to the 5th, because the 1st leaves no room if payroll slips by a day. A debit on the 4th may be priced at the 4th's NAV or a working day later, depending on when the money reaches the scheme; the what is a SIP guide explains the 3 pm cut-off. It fits mapping your outflows by date: savings leave soon after pay lands, and a few days' room covers a late credit.

Does spreading SIPs across the month help rupee cost averaging?

Rupee cost averaging comes from buying every month through rises and falls, not from the day within the month. Putting all ₹60,000 on the 2nd would have ended ₹39,814 lower than Tarun's four dates over 20 years and ₹28,515 higher over 10, noise both ways. Several dates suit only money that arrives on several dates. As pay rises, a step-up SIP changes the amount, not the day.

Dhi looks at your cash flow alongside your net worth, protection and goals, and answers questions about your SIPs and your salary from your own numbers. Dhi maps your investments to goals, nudges you when something needs attention and earns no commissions.

Frequently asked questions

Each ELSS instalment is locked in for three years from the date its units are allotted, so a monthly SIP frees one instalment a month, three years after each was bought. The date of the month decides which day each instalment unlocks; it does not shorten the lock-in.
Some platforms let you edit the date of a running SIP; on others you stop it and register a new one on the new date. A stop request takes up to two working days to process, so make it a few working days before the old debit date.
That month's units are not bought, but the SIP carries on next month unless this was the third failed debit in a row (the second for a quarterly SIP), which cancels it. The money stays in your account, less the bank's return charge. You can invest the same amount by hand as a one-time purchase in the same scheme, and the fund house or its registrar must tell you after the first failure, so use that message as the cue to fix the date or the balance before the next debit.

This is general information for salaried individuals in India, not personalised financial advice.