What is a sinking fund?

Money set aside monthly for a specific known future cost. Unlike an emergency fund, it is meant to be spent, on something you already expect.

One sinking-fund account or several?

One account with a written list of what the balance is earmarked for is enough for most people, and much less admin than five accounts.

What if a big cost arrives before I have saved for it?

Cover it from the buffer if it is genuinely unavoidable, then rebuild the buffer as your first priority and add the item to next year's list.

How to plan for big expenses without breaking your budget

Car service, insurance renewal, school costs, Christmas, a holiday, a new laptop when the old one dies. These rarely wreck a budget because they are unaffordable — they wreck it because they were not on the list, and they all seem to land in the same month.

Author: Sergey Kozyrev — economics background and professional experience with payments and financial processes.

Last reviewed: September 17, 2026

General information only, not individualized financial advice.

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Write the twelve-month list

Sit down once and list every non-monthly cost you can foresee for the next year, with a rough amount and the month it falls in. Most people find between eight and fifteen items, and the total is usually a genuine surprise.

annual insurance, road tax, professional fees
car service, tyres, MOT-style inspections
holidays, flights home, weddings you already know about
birthdays and Christmas, taken together rather than one at a time
replacement cycles: phone, laptop, washing machine, boiler service

Turn each one into a monthly slice

Divide each amount by the number of months until it is due, and add the slices together. A 480 insurance bill due in eight months is 60 a month; a 1,200 holiday in ten months is 120. That combined figure is your sinking fund contribution.

Hold it in a separate account so it is not accidentally spent, and let each item draw down from it when the bill arrives. Nothing about this is clever — it simply moves the pain from one month to twelve.

Check when they collide

The awkward part is rarely a single expense. It is March, when the car service, the insurance renewal and a family birthday arrive within ten days of each other, in a month that also has five weekends.

Placing each cost on its real date and following the balance forward shows those collisions months ahead. The fix is usually easy at that distance: move the service by two weeks, pay the insurance annually in a lighter month, or start the sinking fund a month earlier.

Decide the funding rule before you need it

For anything that has not been saved for yet, decide in advance what you will do: delay it, part-fund it from the buffer, or spread it with a payment plan you deliberately chose. The bad version is a rushed decision made under pressure at the till.

Keep the emergency fund out of this. A holiday is not an emergency, and a sinking fund exists precisely so that planned costs never touch the money reserved for genuine ones.

Review the list quarterly

Prices move, plans change, and new items appear the moment a friend announces a wedding abroad. A short quarterly review keeps the list honest and lets you adjust the monthly slice before the shortfall becomes real.

Over a couple of years, this is the change that makes budgets stop failing: the large costs stop being interruptions and start being ordinary lines in the plan.

Common questions

What is a sinking fund?: Money set aside monthly for a specific known future cost. Unlike an emergency fund, it is meant to be spent, on something you already expect.
One sinking-fund account or several?: One account with a written list of what the balance is earmarked for is enough for most people, and much less admin than five accounts.
What if a big cost arrives before I have saved for it?: Cover it from the buffer if it is genuinely unavoidable, then rebuild the buffer as your first priority and add the item to next year's list.