Sinking Funds: The Budget Habit That Kills Surprise Bills

A budget that works every month and collapses three times a year is not a working budget. The cause is almost never overspending. It is that some real costs arrive annually while the budget only thinks in months.

The problem with monthly budgets

A monthly budget quietly assumes every expense is monthly. Rent, groceries and transport fit that shape. A great many costs do not: annual insurance renewals, road tax, professional memberships, the boiler service, school uniforms, birthdays, holidays and the whole of December.

Because these are invisible in a typical month, the money that should be reserved for them looks like surplus. It gets spent, correctly according to the budget, and then the bill arrives and goes on a credit card. The household concludes it is bad with money. It is not. Its budget is using the wrong time period.

What a sinking fund is

A sinking fund is money set aside gradually for a known future cost. It is not an emergency fund. An emergency fund covers the things you cannot predict; a sinking fund covers the things you can, and the whole point is that they stop competing.

Setting them up

1. List every non-monthly cost from the last twelve months. Statements again, not memory. Include the ones you paid on a card and regretted.
2. Write the annual amount next to each, then divide by twelve. That number is what the cost actually is per month; it always was.
3. Add the monthly figures together. This total is the single most useful number in the exercise, and it is usually larger than people expect.
4. Automate one transfer on payday for the combined total, into an account separate from spending money.

One transfer, not eight. Splitting each category into its own account is satisfying for about two months and then becomes admin you abandon. Keep a single pot and track the categories on a note or a spreadsheet.

Where to keep the money

• Separate from your current account, so it is not visible as spendable balance. Visibility is what kills it.
• Instantly accessible. This money has known jobs on known dates. Locking it away for a slightly better return defeats the purpose.
• Earning something. It sits there for an average of six months, so an interest-bearing account is worth the ten minutes it takes to open.

The first year is the hard one

You will be building the fund while some of this year's bills still arrive, so the first twelve months feel like paying twice. They are not: you are paying this year's costs and pre-funding next year's at the same time. If that is too much at once, start with a half-sized transfer and raise it after six months. From the second year onward the annual bills stop being events. They become transfers out of an account that was always expecting them.