Short answer: there is no best date to start a SIP, and any page that promises you one is selling a myth. Long-term backtests across decades of Indian market data all reach the same conclusion. The gap between the best and worst SIP date is around 0.07 to 0.15 percent, which on a ₹12 lakh investment works out to roughly ₹2,300. That is a rounding error, not a strategy. Pick a date close to your salary credit so you never miss an installment, and stop worrying about it. Here is the honest, data-backed answer that most articles avoid giving.
The myth everyone repeats
Search for the best SIP date and you will find confident claims: invest on the 1st, no, the 7th, actually the last Thursday when the market is volatile, or only on days the market dips. Each sounds clever. Each implies you can squeeze out extra returns by picking the right day of the month. It is a tempting idea, because it feels like control. But it does not survive contact with actual data. When researchers backtest these theories over long periods, the supposed advantage simply vanishes.
What the backtests actually found
Several independent studies have run SIPs on every date of the month across long stretches of market history. The results are strikingly consistent.
| Backtest | Best vs worst date | Difference |
|---|---|---|
| Nifty 100, 10 years (2013 to 2022) | Best on the 25th (10.58% XIRR), worst on the 1st (10.43%) | About 0.15%, roughly ₹2,300 on ₹12 lakh invested |
| BSE Sensex, 10-year rolling (1996 to 2024) | Best on the 1st or 23rd (15.63%), worst on the 9th or 10th (15.56%) | About 0.07% |
| Study across 27-plus years | Returns ranged from 13.55% to 13.62% | About 0.07% |
Read those difference figures again. We are talking about seven-hundredths of a percent over a decade or more. And here is the giveaway: the winning date is not even the same across studies. One backtest crowns the 25th, another the 1st, another the 23rd. If a truly best date existed, it would show up again and again. It does not, because the small differences are just random noise from whichever period you happen to measure. The popular belief that investing on the monthly F&O expiry day beats other dates also fails to hold up in the data. These returns are measured as XIRR, the correct way to judge a series of investments, which we explain in XIRR vs CAGR.
Why the date barely matters
The reason is the whole point of a SIP: rupee cost averaging. When you invest every month for years, you buy units at hundreds of different market levels, some high, some low. Your average purchase price is:
\text{Average Cost} = \frac{\text{Total Invested}}{\text{Total Units Bought}}Over 120 or 240 installments, whether a particular month’s purchase happened on the 5th or the 25th changes almost nothing, because it is one small data point among hundreds. The highs and lows within a month wash out completely across years. Trying to optimize the day of the month is like trying to change the temperature of the ocean with an ice cube. The mechanism is designed to make timing irrelevant, and it works.
The one date rule that does matter
If the return difference is noise, is there any smart way to choose? Yes, and it has nothing to do with markets. Set your SIP date a day or two after your salary is credited. This single habit does the only thing that actually protects your returns: it makes sure the money is in your account when the auto-debit runs, so your SIP never bounces. A missed installment costs you real money in lost compounding and, after three in a row, can even cancel your SIP, as we cover in what happens if you miss a SIP installment. Investing right after payday, before the money gets spent, beats any market-timing trick.
What actually moves your returns
If you have energy to spend optimizing your SIP, spend it on the things that genuinely matter, because their impact dwarfs the date by a thousand times.
- Starting early. A few years of extra compounding changes your corpus by lakhs, not by ₹2,300. Time in the market beats timing the market every time, as the numbers in our cost of delay by age analysis show.
- Staying consistent. Never skipping installments matters far more than which day you invest on. Consistency is the engine.
- Investing enough. The amount you invest drives your outcome. Raising your SIP as your income grows moves the needle hugely.
- Choosing the right fund and plan. A low-cost direct plan in a solid fund beats obsessing over dates. Model your plan in our SIP calculator.
The bottom line
The best date to start a SIP is a question with a refreshingly boring answer: it does not matter. Decades of backtests show the gap between the best and worst date is around 0.07 percent, a difference you will never notice. So pick a date just after your salary lands, so your SIP always goes through, and then forget about it. The energy you save is far better spent starting early, staying consistent, and investing more. That is where real returns are made, not in the calendar.
There is no single best date. Long-term backtests show the difference between the best and worst SIP date is only about 0.07 to 0.15 percent over 10 or more years, which is negligible. The smart choice is a date just after your salary credit, so your SIP never bounces due to low balance.
Barely. Across studies spanning 10 to 27 years of Indian market data, the gap between the highest and lowest returning dates was only around 0.07 percent in XIRR. On a ₹12 lakh investment that is roughly ₹2,300. The date you choose has almost no effect on your long-term wealth.
Not necessarily. In one 10-year backtest the 1st was actually the worst date, while in another it tied for the best. The winning date changes with the period studied, which proves there is no reliably best day. The differences are random noise, not a pattern you can exploit.
For most investors, no. Trying to time dips means predicting the market, which is very hard to do consistently. A SIP already buys more units when prices are low through rupee cost averaging, so a fixed date on autopilot usually beats waiting for the perfect dip that may never come.
You can, but it makes almost no difference. Splitting a SIP across two dates only smooths timing slightly, and backtests show the benefit is negligible over the long term. It is a personal preference, not a return booster, so do it only if it feels more comfortable.
Starting early, staying consistent, and investing enough matter far more than the date. These can change your final corpus by lakhs, while the date changes it by a few thousand rupees at most. Focus on time in the market and never missing installments, not on picking a perfect day.
