Sinking funds: no more "surprise" expenses
Christmas comes every December. The car needs a service every year. Your phone will break one day. These costs are not emergencies — you know they are coming — yet they wreck many budgets because they arrive in one big bill. A sinking fund fixes that: you save a small amount every month for one specific, expected cost, so when the bill arrives, the money is already there.
Where the name comes from
The term comes from corporate finance. A company that issues a bond often promises to put money into a sinking fund every year, so it can repay the bond at maturity without a crisis. The debt "sinks" a little every year. Your household does the same thing with gifts, holidays and car repairs.
Sinking fund or emergency fund?
| Emergency fund | Sinking fund | |
|---|---|---|
| For | The unknown: job loss, urgent repairs, medical bills | The known: gifts, holidays, insurance, a new laptop |
| Do you know the amount? | No | Roughly, yes |
| Do you know the date? | No | Usually, yes |
| Spending it is… | A rare event; refill it right after | The plan; that's what it's for |
| Size | 3–6 months of needs (step 1) | The sum of your upcoming costs |
Without sinking funds, the emergency fund quietly turns into a "Christmas and car service" fund, and it's empty when a real emergency comes.
The formula
A $600 Christmas budget, with nothing saved and 12 months to go, needs $50 a month. If you start late, with only 8 months to go, it needs $75 a month this year, then $50 a month from next year on. Starting early makes every sinking fund cheaper.
For costs that come every few years, divide by the full period: a $720 phone that lasts 3 years is $720 ÷ 36 = $20 a month.
Sam's sinking funds
Sam, from our money plan, already has one sinking fund without calling it that: the $150 a month holiday fund. Going through last year's bank statements, Sam finds four more expenses that came as one big bill and ended up on a credit card:
Before, these $1,920 a year (600 + 360 + 240 + 720) were "unexpected" and went on a credit card. Now they are just five lines in the budget.
How to set them up
- List the irregular costs of the last 12 months. Your bank statement is the best memory: look for any bill bigger than a normal week of spending.
- Add the ones you know are coming: a wedding next summer, a car service, a new laptop for school.
- Calculate the monthly amount with the formula above and add each one as a line in your budget.
- Keep the money apart. One savings account is enough. Many banks let you create named "pots", "spaces" or sub-accounts for free: one per fund. If yours does not, a simple spreadsheet can track how much of the balance belongs to each fund.
- Automate it. A standing order on payday, like the emergency fund.
- Spend it without guilt when the bill arrives. That's the whole point.
Common sinking funds
🏠 Home & car
Car service and tyres, car insurance paid yearly, road tax, home repairs, a new washing machine, furniture.
🎁 Life & family
Gifts, holidays, weddings, school supplies, children's activities, a pet's vet bills.
💻 Things that wear out
Phone, laptop, glasses, winter clothes, a bike. Divide the price by how many years it usually lasts.
🧾 Yearly bills
Property tax, annual subscriptions, professional fees, accountant, bank card fees.
Show the answer
(840 − 140) ÷ 7 = $100 a month until the bill. After that, the next payment is 12 months away, so 840 ÷ 12 = $70 a month. Starting on time is cheaper: a fund that is always 12 months ahead costs $70 a month, not $100.