Irregular income does not need an irregular SIP. The workable answer: hold 9–12 months of expenses as a buffer, pay yourself a fixed "salary" from it, and set the SIP at about 15–20% of that salary, not of whatever landed this month.
"Invest 20% of your income" assumes the same amount arrives every month. If you earn ₹40,000 in one month and ₹1,60,000 in the next, a percentage-of-income SIP bounces around, and the bank mandate fails in the lean months. A failed debit is the real danger: it breaks the habit exactly when the habit matters.
Salaried people usually keep 3–6 months of expenses. With variable income, the buffer also has to cover the lean stretch, so 9–12 months is the more common aim. Keep it in low-risk, easy-access options, and build it before you raise the SIP.
| Monthly expenses | Buffer (9 months) | Buffer (12 months) |
|---|---|---|
| ₹40,000 | ₹3.6 lakh | ₹4.8 lakh |
| ₹60,000 | ₹5.4 lakh | ₹7.2 lakh |
| ₹80,000 | ₹7.2 lakh | ₹9.6 lakh |
Decide the rule in advance so you are not tempted to spend the windfall. One simple split for months above your salary:
Nobody pays your health cover or retirement contribution for you, so budget both as fixed costs inside your salary. Term cover and a health base plus top-up matter more when income stops the moment you do. Retirement is yours alone to fund; a long-term equity assumption of about 11–12% only works if the SIP actually runs for decades.
In the plan, each goal gets its own SIP, so a fixed salary can be mapped to goals one by one. The equity share then de-risks automatically as each goal nears. If the mandate amount is tied to your floor, a lean quarter will not break it.
Q. Should I skip the SIP in a bad month?
A. If the buffer is intact, usually no. That is what the buffer is for. Pausing is a decision for a prolonged income loss, not one slow month.
Q. Is a lump sum better than a SIP when income is irregular?
A. A mix works. The floor-based SIP gives the habit; the lump sums from strong months add to it. Returns are never guaranteed either way.
Q. Where do I keep the buffer?
A. In low-risk, easily withdrawable options. Safety and access matter more than return here.
Q. How do I handle tax on variable income?
A. Keep a separate tax set-aside from every receipt. Rules and due dates change, so confirm the current year's details with a CA.
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