Sinking funds: a simple way to pay irregular expenses

The expense that was never a surprise

Most households can budget for rent, groceries and EMIs. The month that breaks the budget is the one with the car insurance premium, the school fees and the festival shopping all landing together. None of these is an emergency. You knew the date a year ago. They simply arrive as a lump, and a monthly budget cannot absorb a lump.

A sinking fund fixes this. You list the big irregular bills, divide each by 12 and move that amount into a separate pot every month. When the bill arrives, the money is already there. Nothing "sinks" in the sense of being lost: it is a fund that is drawn down to zero on purpose.

Step 1: list the lumps

Go back over a year of bank and card statements and write down every expense that is not monthly. Typical ones: vehicle insurance, health and term premiums, school or tuition fees, annual subscriptions, property tax, festival and gifts, vehicle servicing, travel, and a repair allowance for the home or appliances. If a bill is not on the list, the first time it hits will tell you.

Step 2: do the arithmetic

An illustration with assumed figures:

That is ₹18,000 a month, or ₹2.16 lakh over the year. For a household with a take-home of ₹80,000, the transfer is 22.5% of pay. It looks like a lot until you remember it was already being spent, just not on a schedule.

If the total is too high, cut a category before you cut the habit. A vacation of ₹30,000 instead of ₹60,000 lowers the monthly figure by ₹2,500. Our 50-30-20 budget rule shows where this slots in: a sinking-fund transfer is a "want" and "need" mixture, and it is cleaner to count each bill in its own bucket.

Step 3: choose where the money sits

The two rules are that you can reach it when the bill comes, and that it cannot fall in value. For money due within a year:

• A separate savings account. The simplest, and it works well with a standing instruction on salary day. Because it is not your main account, you will not spend it by accident. Deposits are insured up to ₹5 lakh per depositor per bank by the DICGC, ₹5 lakh at the time of writing; check the current limit.
• A bank recurring deposit. Locks the discipline in, with a fixed maturity that you can match to the bill. Many banks allow tenures from a few months; check the minimum and the penalty for breaking it. The RD calculator shows what a given rate earns.
• A liquid fund, for amounts needed in six to twelve months. It can earn a little more than a savings account, and it is a market-linked product that can move slightly. Read overnight vs liquid vs ultra short funds and browse liquid funds before you decide.

For bills more than three years away, such as a child's college fees, you are not saving for a "sinking" expense but for a goal, and equity may have a role; see goal-based investing and the goal calculator.

The post office also runs a recurring deposit scheme if you prefer a government-backed option; check the current tenure and rate there.

When a bill is bigger than planned

Premiums rise, fees are revised and repairs overshoot. Build a margin of 10% into each line when you set the monthly figure, and revisit the table the day a new premium notice or fee circular arrives. If a bill still exceeds the pot, take the shortfall from the next category with slack, such as the holiday line, rather than from the emergency fund. The sinking fund works because every rupee has a named job, so moving money between jobs should be a deliberate choice.

Keep it separate from the emergency fund

This is the mistake that undoes the system. If the car insurance and the emergency fund share one account, a premium payment looks like a withdrawal from your safety net, and the net quietly shrinks. Keep them apart, ideally in separate accounts with names such as "Sinking fund" so the balance tells you the truth. The emergency fund calculator sets a target for the second pot, and where to keep an emergency fund explains the options. If your income is itself irregular, the version for you is an emergency fund for freelancers.

Make it run itself

The system fails in two ways: you stop topping it up when a month is tight, or you borrow from it and never repay. Treat the transfer like an EMI that cannot be skipped, and if you do borrow from it, write down the amount and refill it first when the next salary arrives.

1. Open a separate account, or a labelled sub-account.
2. Set a standing instruction for the day after your salary credit.
3. Review once a year, when the new premium letters and fee notices arrive, and reset the monthly figure.
4. When a bill is paid, do not stop the transfer. The next year's pot starts filling straight away.

If a bill comes before the fund is full, because you started late, cover the gap from a one-time transfer, not from a card. A sinking fund that is half-funded still turns a ₹60,000 shock into a ₹30,000 gap, which is easier to manage.

Once the lumps are covered, the leftover money in your budget can go to a SIP without the worry that the next premium will force you to stop it, and the habit of naming a purpose for every rupee makes it easier to track your net worth as it grows.

This post is for education only and is not financial advice. The figures above are assumed for illustration; deposit insurance limits, interest rates and scheme terms change, so verify before you rely on them.