Most budgets are built around the bills that arrive every month: rent or the mortgage, the phone, groceries, transit. Then a month comes along with a car insurance renewal, a registration fee, a dental bill and two birthdays, and a budget that worked fine in September falls apart in March.

None of those costs are emergencies. You knew they were coming, often to the week. They just don't come often enough to stay on your radar, so they end up on a credit card or come out of savings that were meant for something else.

A sinking fund fixes that. It's money you set aside a little at a time for a cost you know is coming, so that when the bill arrives, the money is already waiting.

Find your once-a-year bills

Start with the last twelve months of bank and credit card statements. You're looking for anything that came out once, twice or a few times a year rather than every month. Reading your own bank statement walks through how to spot them, including merchant names that don't look like the company you paid.

Common ones include car insurance if you pay it yearly, licence plate or registration renewals, home or tenant insurance, property tax if it isn't collected with your mortgage payment, annual memberships and app subscriptions, the spring and fall tire changeover, car maintenance, dental and eye care your plan doesn't cover, children's sports and school fees, and birthdays. Your list will be different, and that's the point: build it from what you actually paid, not from a template.

Some costs don't have a fixed date but come around anyway, like car repairs or replacing a phone. If you can put a rough yearly figure on them, they belong on the list too.

Turn the yearly total into a monthly amount

Write a yearly amount beside each item, add them up and divide by 12. Take a hypothetical household that pays $1,200 for car insurance, $120 for registration, $200 for two tire changeovers, $600 for car maintenance, $300 for dental and eye care, $480 for birthdays and gifts, $180 for annual subscriptions and $720 for kids' activities. That's $3,800 a year.

Divided by 12, it's about $317 a month, or about $146 a paycheque if you're paid every two weeks. That's a real number, but it's far easier to plan around than $1,200 leaving your account in a single week.

Catch up on bills that are due soon

The monthly figure assumes a full year to save, and some bills will come sooner. If that $1,200 insurance renewal is due in four months, $100 a month won't be enough. For that one bill, set aside $300 a month until it's paid, then drop back to $100 a month for next year's renewal.

If the catch-up amounts don't fit, it's better to find out now. You might trim the list, ask your insurer whether monthly payments are an option and what they cost, or accept that one bill will go on a card this year and decide how quickly you'll pay it off.

Where to keep it

Keep the money in a separate savings account, not in chequing. If it sits beside your bill money, your balance will tell you that you have more to spend than you really do, and the insurance money slowly turns into groceries and takeout.

Set up an automatic transfer on payday so it happens before you can spend it. One account with a simple running list of what it's for is usually enough. Some people prefer a separate account for each goal. Either works, as long as you know what each dollar is set aside for.

A sinking fund isn't an emergency fund

The two can sit in similar accounts, but they do different jobs. A sinking fund is for costs you can predict. An emergency fund is for the ones you can't, like losing your job or a sudden move. If your car insurance comes out of your emergency fund every year, you don't really have an emergency fund. You have a sinking fund with the wrong name.

Check it once a month

Once a month, look at what's due in the next few months and whether the balance will cover it. If a bill went up at renewal, raise your monthly amount to match. A 15-minute monthly money review is a good time to do it.

How SmartSpend AI helps

SmartSpend AI, now in private testing, works from the PDF bank and credit card statements you already download, without a bank login. You can name a goal like car costs or next year's insurance, set a target and a date, and it works out the monthly amount, fits it into your budget and checks your statements for the transfers that show you're on track.

It also shows what's due in the weeks ahead, picks out subscriptions and fixed bills from their billing rhythm and flags price increases, so a higher renewal doesn't slip past you. You can join the waitlist to hear when it launches.