An emergency fund is for the things you did not see coming. A sinking fund is for the things you did — the annual, quarterly and seasonal costs that are entirely predictable and still manage to arrive as a shock.
List the costs that skip months
Write down every expense that does not arrive monthly, with its rough amount and when it falls due. Most households find between eight and fifteen. The list itself is usually the most useful part of the exercise, because these costs are the ones a monthly budget structurally cannot see.
- Car registration, CTP, servicing and tyres
- Home, contents, car and health insurance excesses
- Christmas, birthdays and school costs
- Dentist, optometrist and the annual vet visit
- Annual subscriptions and professional memberships
Divide by the months, not by hope
Add the yearly total and divide by twelve. That figure is what these costs genuinely cost you each month — it was always true, it was just never written down. A household with A$900 rego, A$1,400 insurance and A$800 of Christmas is carrying about A$260 a month it had not budgeted for.
One fund or several
A single pooled fund is simpler and works well if you are disciplined about not treating a healthy balance as spare. Separate funds per purpose take more setup but make it obvious when the car money has been quietly spent on Christmas. Start pooled; split only the categories that keep getting raided.
Why this is the cheapest habit in budgeting
Irregular bills are the most common reason people reach for a credit card or a buy-now-pay-later plan while otherwise budgeting well. Funding them in advance removes the interest, the late fees and the month where everything else has to shrink to absorb a bill that was never a surprise.
Useful Australian sources
Rules and figures can change. These official or public-interest sources are the best place to check current information.