How a SIP actually works - and why the start date matters less than you think

Most conversations about SIPs skip the mechanics and jump straight to the outcome. That is a shame, because the mechanics are genuinely simple, and understanding them is what helps people stay invested when markets get uncomfortable.

What happens each month

A Systematic Investment Plan is a standing instruction. On a date you choose, a fixed amount moves from your bank account into a mutual fund scheme, and you are allotted units at that day's net asset value. Nothing more dramatic than that happens. There is no separate product called a SIP - it is simply a way of investing into a scheme.

Because the amount is fixed and the price is not, the number of units you receive changes every month. When markets fall, the same instalment buys more units. When markets rise, it buys fewer. Over many months your average purchase price settles somewhere in between the highs and the lows.

What rupee cost averaging does, and does not, do

This averaging effect is often described as though it removes risk. It does not. If the scheme you are invested in performs poorly over your entire holding period, averaging will not rescue the outcome. What it does remove is the need to be right about timing - and for most working investors, that is the harder problem.

Why the start date is a distraction

We are often asked whether the 1st, the 10th or the 25th is the better SIP date, or whether one should wait for a correction before starting. Over a long investment period, the difference between SIP dates tends to be small, because you are buying across dozens of market levels anyway.

Waiting, on the other hand, has a real cost. Every month spent waiting for a better entry point is a month of instalments not made. The investor who starts on an ordinary Tuesday and keeps going usually ends up in a better position than the one still waiting for the ideal week.

Getting the instalment right

The most common reason SIPs stop is not a market fall - it is an instalment that was set too high in a moment of enthusiasm. A sustainable amount that survives a bad month at work is worth more than an ambitious one that gets cancelled in the first year.

• Pick an amount you can maintain even in a lean month
• Increase it deliberately when your income rises, rather than starting high
• Link it to a goal, so you know what you are protecting when markets wobble
• Review it once a year instead of reacting to every market headline

The part people underrate

The mathematics of a SIP is ordinary. The behaviour is the hard part - continuing the instalment in a month when the portfolio value is lower than the amount you have put in. That is precisely when the instalment is buying the most units, and it is also when most people want to stop.

If you would like help deciding an instalment amount, a time horizon and the scheme categories that suit your goals, our team in Manimajra, Chandigarh is happy to talk it through.