Most budgets break on the same few bills: the car service, the insurance renewal, December. None of them are surprises; they just do not arrive every month. A sinking fund is the simple fix. Here is what one is, how to set one up, and a worked example with all the arithmetic shown.
What are sinking funds?
A sinking fund is money you set aside a little at a time for a cost you already know is coming. Instead of finding $540 in the month the car needs a service, you put $45 aside every month, and when the bill arrives the money is waiting.
The idea is old and the arithmetic is simple. What makes it work is a change in how the cost feels. A yearly bill paid in one go feels like an emergency. The same bill paid in twelve small pieces is just another line in the monthly budget.
Sinking funds are not the same as an emergency fund. An emergency fund is for costs you cannot predict. A sinking fund is for costs you can, even if they come at odd times. If you pay for predictable bills out of your emergency fund, it is never there when the real emergency comes.
A sinking funds list to start from
Go through last year's bank statements and note every cost that did not come monthly. Most lists include some of these:
- Car: servicing, tyres, registration or road tax, insurance if paid yearly.
- Gifts and holidays: birthdays, Christmas, weddings.
- Annual subscriptions: software, memberships, streaming paid yearly.
- Insurance: home, contents, pet, travel.
- Home repairs: the boiler service, a new appliance, decorating.
- Medical and dental: check-ups, glasses, prescriptions.
- Travel: a summer trip, visiting family.
- Clothes and tech: a winter coat, a phone or laptop that will need replacing.
Do not try to fund all of them on day one. Start with the two or three that hurt most last year, and add the rest as the budget allows.
How to set up sinking funds, step by step
- List each cost and its yearly amount. Use last year's real figure where you have it. If it varies, round up.
- Divide by twelve. That is the monthly amount to set aside.
- Add up the monthly amounts. This total is one new line in your monthly budget.
- Check it fits. If it does not, fund the nearest bills first and lower the rest.
- Automate it. A standing transfer on payday means you decide once, not every month.
- Pay the bill from the fund. When the cost arrives, move the money back and pay it. That is the whole point.
A worked example, with the arithmetic
Say these are your irregular costs for a year. The figures are illustrative; use your own.
| Fund | Per year | ÷ 12 per month |
|---|---|---|
| Car (service, tyres, registration) | $540 | $45 |
| Car insurance | $900 | $75 |
| Gifts and holidays | $720 | $60 |
| Annual subscriptions | $156 | $13 |
| Medical and dental | $300 | $25 |
| Total | $2,616 | $218 |
The yearly costs add up to 540 + 900 + 720 + 156 + 300 = $2,616. Divided by twelve, that is $218 a month, which matches the monthly column: 45 + 75 + 60 + 13 + 25 = 218.
That number is the honest cost of these bills. Without sinking funds you still pay $2,616 a year; you just pay it in lumps, in whichever months the bills happen to land.
Starting late: when the bill is less than a year away
The divide-by-twelve rule assumes you have twelve months. Often you do not. Say the car insurance renews in five months and you are starting from nothing:
Needed: $900 in 5 months.
Until the renewal: $900 ÷ 5 = $180 a month.
After the renewal: back to $900 ÷ 12 = $75 a month, for next year's bill.
If $180 a month is too much, set aside what you can and plan to cover the gap at renewal, or look at paying monthly for one year. The second year is always easier than the first.
Annual subscriptions: check before you fund
In the example, $156 a year of annual subscriptions is $13 a month. Before you fund them, list every one with its cost and renewal date, and decide whether each is worth keeping. A subscription you forgot about is still one you are choosing to pay for. Cancelling one $60 renewal lowers the fund by $5 a month.
Keeping sinking funds simple
- Separate the money. A savings pot or second account keeps it out of everyday spending.
- Keep a written list. If all your funds share one account, a list of what belongs to each stops one fund quietly paying for another.
- Review once a year. Prices change. Update each yearly amount when the bill arrives, and redo the division.
- Treat the monthly total as a bill. It goes in the budget alongside rent and utilities, not after them.
This is general budgeting education, not financial advice. The right funds and amounts depend on your own bills and income.
The kit used in this guide
The SagaLeaf Money Reset Budget Kit has a sinking funds page in the PDF and a Sinking funds sheet in the spreadsheet. Type the yearly amount for each cost and the sheet divides it by twelve and totals what to set aside each month. It starts with car, gifts and holidays, travel, insurance, home repairs, medical and dental, clothes and tech, with room for your own.
The 28-page PDF also has a subscriptions audit, a debt plan, savings goals, a monthly budget template and twelve monthly pages. The spreadsheet totals each month by category from a single list of transactions. The PDF comes in US Letter and A4 for GoodNotes, Notability or print, and the spreadsheet opens in Excel, Google Sheets and Numbers.
Questions people ask
- What is a sinking fund?
- Money you set aside a little at a time for a cost you know is coming, such as a car service, gifts or an annual subscription. When the bill arrives, the money is already there.
- How is a sinking fund different from an emergency fund?
- A sinking fund is for costs you can predict, even if they are irregular. An emergency fund is for the ones you cannot, like a job loss or a sudden repair. Keeping them separate stops planned costs from quietly using up your safety net.
- How do I calculate a sinking fund?
- Divide the yearly cost by twelve to get the monthly amount. If the bill is due sooner than twelve months away, divide what you still need by the number of months left instead.
- Where should I keep sinking funds?
- Somewhere separate from your everyday spending, so the money is not spent by accident. Many banks let you open more than one savings pot or account; one pot holding all of them with a written list of what belongs to each also works.