Sinking funds: what they are and how to use them

A sinking fund is money you set aside a little at a time for a cost you know is coming. It's the quiet trick that stops Christmas, the car service, or the annual insurance bill from blowing a hole in your month.

The problem sinking funds solve

Some costs aren't monthly, but they're not surprises either. You know Christmas happens in December. You know the car needs an MOT. You know the insurance renews. Yet because they don't arrive every month, they're easy to forget, until they land all at once and force you onto a credit card.

A sinking fund fixes this by spreading the cost across the months leading up to it. Instead of finding £600 in December, you set aside £50 a month all year and the bill is already paid for.

Common sinking funds

Fund	Example total	Monthly (over 12)
Christmas	£600	£50
Car maintenance & MOT	£480	£40
Annual insurance	£360	£30
Birthdays & gifts	£240	£20

You can run several at once. The maths never changes: total cost ÷ months until due = monthly amount.

Sinking fund vs emergency fund

They're easy to confuse, but they do different jobs:

• Sinking fund: for planned costs you can see coming: Christmas, MOT, renewals.
• Emergency fund: for genuine surprises: job loss, a broken boiler, an urgent repair.

Keep them separate. If you raid your emergency fund every December, it isn't really an emergency fund. It's a Christmas fund wearing a disguise.

How to set them up

1. List the irregular costs you know are coming over the next year.
2. Estimate a total for each one.
3. Divide each total by the months until it's due to get a monthly amount.
4. Automate those transfers, ideally into clearly labelled pots or a separate savings account.

The bottom line

Sinking funds turn scary one-off bills into small, predictable monthly amounts. List your known future costs, divide each by its timeframe, and let the funds fill quietly in the background. When the bill arrives, it's already handled.