ToolsSIP check
Does timing change a SIP?
Most timing tweaks move a ten-year SIP by a few tenths of a point at most. Buying after a 2% fall left a Nifty 500 SIP 0.29 points behind at the median; a weekly SIP finished 0.05 points ahead of a monthly one; starting at an all-time high cost 0.33 points against starting after a 10% fall. The one rule that came out ahead, waiting for a 20% fall, did so on the back of two crashes and spent years in cash.
Written for SIP investors tempted to time their instalments. Data to 6 Oct 2026.
Buying the dips
The usual advice, 'add more when the market falls', usually comes with more money: of course a SIP with extra money in it ends bigger. The fair test keeps the money the same. Each month's Rs 10,000 goes into a liquid fund, and the whole balance moves into the index on the first session after the signal. Daily-fall rules trigger often; peak-to-trough rules can leave the money waiting for years. Anything still waiting at the end counts at its liquid-fund value.
Waiting for a dip, against investing every month
Median difference in 10-year after-tax XIRR against the plain SIP on the same start months
How to read it. Left of zero, waiting lost. Rules that trigger on daily falls cost a little: buying after any 1% fall trailed in 100% of Nifty 500 windows, because a week or two in cash is a week or two out of the market. Waiting for a 3% fall cost the Smallcap 250 1.76 points. Waiting for a 20% fall finished 0.73 points ahead in the Nifty 500 and 1.00 points ahead in the Nifty 50, on the strength of two crashes inside the sample; the median window bought just 13 times and ended with Rs 4.8 lakh still in cash.
Waiting for a dip, against investing every month. Bar chart of 5 items. Nifty 50: highest When 20% below the peak at +1.00 pts, lowest After a 2% fall at −0.21 pts.
Differences are the rule minus the plain SIP, in after-tax XIRR points, at the median window. 'Ahead' is the share of windows in which the rule finished ahead. 'Independent' counts non-overlapping windows; their mean difference is beside it. Overlapping windows are not independent, so read the independent column before the percentages.
| Rule | Portfolio | Years | Median difference | Ahead | Purchases, median | Cash left, median | Ended with cash | Independent | Their mean difference | More |
|---|---|---|---|---|---|---|---|---|---|---|
| After any 1% daily fall | Nifty 50 | 3 | −0.04 pts | 46% | 91 | ₹0 | 16% | 7 | −0.05 pts | |
| After any 1% daily fall | Nifty 50 | 5 | 0.00 pts | 50% | 144 | ₹0 | 18% | 4 | −0.04 pts | |
| After any 1% daily fall | Nifty 50 | 10 | 0.00 pts | 49% | 297 | ₹0 | 22% | 2 | −0.02 pts | |
| After any 1% daily fall | Nifty 500 | 3 | −0.19 pts | 29% | 90 | ₹0 | 14% | 7 | −0.27 pts | |
| After any 1% daily fall | Nifty 500 | 5 | −0.14 pts | 11% | 146 | ₹0 | 16% | 4 | −0.17 pts | |
| After any 1% daily fall | Nifty 500 | 10 | −0.06 pts | 0% | 306 | ₹0 | 18% | 2 | −0.08 pts | |
| After any 1% daily fall | Nifty Smallcap 250 | 3 | −0.38 pts | 24% | 114 | ₹0 | 8% | 7 | −0.43 pts | |
| After any 1% daily fall | Nifty Smallcap 250 | 5 | −0.23 pts | 10% | 192 | ₹0 | 9% | 4 | −0.29 pts | |
| After any 1% daily fall | Nifty Smallcap 250 | 10 | −0.09 pts | 0% | 385 | ₹0 | 9% | 2 | −0.12 pts | |
| After a 2% fall | Nifty 50 | 3 | −0.28 pts | 41% | 24 | ₹10,000 | 62% | 7 | −0.26 pts | |
| After a 2% fall | Nifty 50 | 5 | −0.35 pts | 21% | 39 | ₹10,000 | 68% | 4 | −0.54 pts | |
| After a 2% fall | Nifty 50 | 10 | −0.21 pts | 13% | 72 | ₹20,000 | 72% | 2 | −0.29 pts | |
| After a 2% fall | Nifty 500 | 3 | −0.77 pts | 19% | 21 | ₹10,000 | 61% | 7 | −0.94 pts | |
| After a 2% fall | Nifty 500 | 5 | −0.50 pts | 10% | 35 | ₹10,000 | 67% | 4 | −0.80 pts | |
| After a 2% fall | Nifty 500 | 10 | −0.29 pts | 0% | 66 | ₹20,000 | 70% | 2 | −0.44 pts | |
| After a 2% fall | Nifty Smallcap 250 | 3 | −1.88 pts | 16% | 39 | ₹0 | 45% | 7 | −1.57 pts | |
| After a 2% fall | Nifty Smallcap 250 | 5 | −1.00 pts | 0% | 64 | ₹0 | 49% | 4 | −1.10 pts | |
| After a 2% fall | Nifty Smallcap 250 | 10 | −0.54 pts | 0% | 128 | ₹0 | 48% | 2 | −0.55 pts | |
| After a 3% fall | Nifty 50 | 3 | −0.64 pts | 46% | 4 | ₹60,000 | 86% | 7 | +0.03 pts | |
| After a 3% fall | Nifty 50 | 5 | −0.77 pts | 42% | 13 | ₹80,000 | 92% | 4 | −0.73 pts | |
| After a 3% fall | Nifty 50 | 10 | −0.18 pts | 42% | 20 | ₹80,000 | 91% | 2 | −0.68 pts | |
| After a 3% fall | Nifty 500 | 3 | −0.78 pts | 35% | 5 | ₹60,000 | 85% | 7 | −0.03 pts | |
| After a 3% fall | Nifty 500 | 5 | −0.59 pts | 42% | 12 | ₹80,000 | 91% | 4 | −0.71 pts | |
| After a 3% fall | Nifty 500 | 10 | −0.09 pts | 47% | 21 | ₹80,000 | 90% | 2 | −0.65 pts | |
| After a 3% fall | Nifty Smallcap 250 | 3 | −1.50 pts | 29% | 15 | ₹20,000 | 70% | 7 | −1.28 pts | |
| After a 3% fall | Nifty Smallcap 250 | 5 | −0.71 pts | 28% | 24 | ₹20,000 | 74% | 4 | −2.58 pts | |
| After a 3% fall | Nifty Smallcap 250 | 10 | −1.76 pts | 0% | 50 | ₹20,000 | 72% | 2 | −1.09 pts | |
| When 10% below the peak | Nifty 50 | 3 | −0.02 pts | 49% | 8 | ₹50,000 | 70% | 7 | +1.45 pts | |
| When 10% below the peak | Nifty 50 | 5 | +0.14 pts | 53% | 9 | ₹70,000 | 78% | 4 | +0.25 pts | |
| When 10% below the peak | Nifty 50 | 10 | +0.17 pts | 81% | 31 | ₹1,00,000 | 87% | 2 | +0.10 pts | |
| When 10% below the peak | Nifty 500 | 3 | −0.04 pts | 50% | 7 | ₹40,000 | 66% | 7 | +1.07 pts | |
| When 10% below the peak | Nifty 500 | 5 | +0.11 pts | 51% | 10 | ₹60,000 | 74% | 4 | −0.07 pts | |
| When 10% below the peak | Nifty 500 | 10 | +0.03 pts | 63% | 39 | ₹1,00,000 | 88% | 2 | −0.03 pts | |
| When 10% below the peak | Nifty Smallcap 250 | 3 | −0.26 pts | 21% | 21 | ₹0 | 41% | 7 | −0.67 pts | |
| When 10% below the peak | Nifty Smallcap 250 | 5 | −0.12 pts | 28% | 37 | ₹0 | 46% | 4 | −0.36 pts | |
| When 10% below the peak | Nifty Smallcap 250 | 10 | −0.05 pts | 35% | 79 | ₹20,000 | 59% | 2 | −0.27 pts | |
| When 20% below the peak | Nifty 50 | 3 | +0.16 pts | 52% | 2 | ₹1,90,000 | 88% | 7 | +0.56 pts | |
| When 20% below the peak | Nifty 50 | 5 | +0.28 pts | 54% | 2 | ₹2,30,000 | 96% | 4 | −1.08 pts | |
| When 20% below the peak | Nifty 50 | 10 | +1.00 pts | 93% | 7 | ₹3,30,000 | 98% | 2 | −0.35 pts | |
| When 20% below the peak | Nifty 500 | 3 | −4.26 pts | 35% | 3 | ₹2,70,000 | 83% | 7 | −1.94 pts | |
| When 20% below the peak | Nifty 500 | 5 | −1.80 pts | 38% | 3 | ₹3,30,000 | 92% | 4 | −1.77 pts | |
| When 20% below the peak | Nifty 500 | 10 | +0.73 pts | 57% | 13 | ₹4,80,000 | 98% | 2 | −0.75 pts | |
| When 20% below the peak | Nifty Smallcap 250 | 3 | +0.18 pts | 53% | 17 | ₹10,000 | 52% | 7 | +0.49 pts | |
| When 20% below the peak | Nifty Smallcap 250 | 5 | +0.07 pts | 57% | 29 | ₹30,000 | 59% | 4 | −0.25 pts | |
| When 20% below the peak | Nifty Smallcap 250 | 10 | +0.19 pts | 68% | 69 | ₹80,000 | 76% | 2 | −0.39 pts |
Starting at a high
People put off starting a SIP because the market is at a record. Here every plain Nifty 500 window is grouped by how far the index was below its all-time high on the day of the first instalment. The shaded column is every start month together. Windows inside a group are not independent: almost every start more than 20% below a high falls between 2008 and 2012, so that group is close to one long episode.
SIPs started near a high, and after a fall
Nifty 500, after-tax XIRR by how far below its all-time high the index was at the first instalment
How to read it. At ten years the groups sit almost on top of each other: 12.3% at the median for starts within 2% of a high against 12.6% for starts 10% or more below. The start matters more over short windows: at three years, 28% of starts near a high finished below FDs, and 44% of starts more than 20% below. Over three years, a fall that has not finished can still drag a new SIP down.
SIPs started near a high, and after a fall. 2 horizons, 4 bands. Within 2% of a high: median +11.5%, 58 windows; 2% to 10% below: median +13.2%, 63 windows; 10% to 20% below: median +14.7%, 39 windows; More than 20% below: median +13.1%, 39 windows. All start months: median +13.4%.
Median after-tax XIRR by the index's distance below its high at the first instalment; windows at 10 years; share of 5-year windows below FDs.
| Portfolio | At the start | 5 years, median | 5 years, below FD | 10 years, median | 10-year windows | More |
|---|---|---|---|---|---|---|
| Nifty 50 | Within 2% of a high | 11.5% | 10% | 10.9% | 35 | |
| Nifty 50 | 2% to 10% below | 12.4% | 10% | 12.5% | 40 | |
| Nifty 50 | 10% to 20% below | 12.9% | 0% | 12.1% | 39 | |
| Nifty 50 | More than 20% below | 9.5% | 0% | 11.5% | 25 | |
| Nifty 500 | Within 2% of a high | 11.5% | 10% | 12.3% | 33 | |
| Nifty 500 | 2% to 10% below | 13.2% | 11% | 13.4% | 35 | |
| Nifty 500 | 10% to 20% below | 14.7% | 0% | 13.0% | 35 | |
| Nifty 500 | More than 20% below | 13.1% | 8% | 12.3% | 36 | |
| Nifty Midcap 150 | Within 2% of a high | 15.5% | 6% | 17.1% | 32 | |
| Nifty Midcap 150 | 2% to 10% below | 11.1% | 25% | 17.6% | 27 | |
| Nifty Midcap 150 | 10% to 20% below | 21.6% | 2% | 16.3% | 18 | |
| Nifty Midcap 150 | More than 20% below | 19.8% | 6% | 16.7% | 62 | |
| Nifty Smallcap 250 | Within 2% of a high | 12.8% | 30% | 15.7% | 31 | |
| Nifty Smallcap 250 | 2% to 10% below | 4.8% | 46% | 16.0% | 21 | |
| Nifty Smallcap 250 | 10% to 20% below | 15.4% | 16% | 13.3% | 10 | |
| Nifty Smallcap 250 | More than 20% below | 19.9% | 15% | 14.2% | 77 |
Weekly or monthly
The same Rs 1.2 lakh a year, paid as Rs 2,308 on the first session of each week instead of Rs 10,000 on the first session of each month.
A weekly SIP against a monthly one
Median difference in after-tax XIRR, weekly minus monthly, same start months
How to read it. In the Nifty 500 weekly finished 0.17 points ahead at three years and 0.05 points ahead at ten. A monthly SIP buys only on the first session of the month, which in Indian indices tends to come just after the turn-of-month rise the date study found; a weekly SIP spreads its buying across the month. That is the likely source of the small edge, since weekly money actually goes in later on average.
A weekly SIP against a monthly one. Bar chart of 5 items. 3 years: highest Nifty 500 at +0.17 pts, lowest Four assets, equal quarters at −0.01 pts.
The date of the month
The full table and the tests are on the main SIP page
The original study, here as a chart: the same SIP on different dates of the month, against the 1st.
The SIP date barely matters
Nifty 500: median after-tax XIRR difference against an SIP on the 1st, points
How to read it. Hundredths of a point, mostly. The small gaps at three years come from a turn-of-month effect in Indian indices, and they fade over longer windows.
The SIP date barely matters. Bar chart of 6 items. 3 years: highest Day 25 at +0.48 pts, lowest Day 5 at −0.02 pts.
What I predicted
Written into the specification on 8 October 2026, before any of these numbers existed. Prediction S1, on the date of the month, is graded on the main SIP page.
S6 Failed
Every dip-buying rule trails the plain SIP at the median 10-year window for the Nifty 50 and Nifty 500.
Not every one: when 10% below the peak (Nifty 50, +0.17 pts); when 20% below the peak (Nifty 50, +1.00 pts); when 10% below the peak (Nifty 500, +0.03 pts); when 20% below the peak (Nifty 500, +0.73 pts) finished ahead at the median. Those rules wait in cash for a deep fall and then buy it, and between 2005 and 2026 that meant two falls, 2008 and 2020, so the result rests on two episodes. In between, the cash sat idle: the median 10-year window ended with Rs 4.8 lakh still waiting. The daily-fall rules, which deploy often, all trailed.
S7 Held
A weekly SIP's median 10-year after-tax XIRR is within 0.1 point of the monthly SIP's for every portfolio tested.
The largest median gap at ten years was +0.05 pts. At three years weekly was ahead by up to +0.17 pts, and the gap shrinks as the window lengthens.
S8 Held
Nifty 500 SIPs started within 2% of an all-time high had a median 10-year XIRR within 1.5 points of those started 10% or more below it.
12.3% against 12.6%, a gap of +0.33 pts, across 33 and 71 overlapping windows.
Historical research on index portfolios, not investment advice. Returns are after fund costs; 'after tax' applies Indian capital-gains rules by date for a 30% slab investor and sells everything at the end. Most factor, mid-cap and small-cap index history before each index's launch date is back-tested by NSE. One 21-year sample, domestic assets only.
The workings
Data
Every chart has a table view, a CSV download and a link to its published JSON. Bundles are listed in data status.