Sinking Funds: The List, the Maths and a Tracker

Hey folks, it's Ren here.

The envelope is on the doormat before you have found your keys. The window is clear plastic, the print is red, and the amount is the one you have been meaning to think about since March.

Nothing about it is a surprise. The date has been the same every year. What changes is whether the money is already sitting somewhere with its name on it.

Sinking funds are how that envelope stops being a bad moment. You split the yearly cost into twelve small pieces, set one aside each month, and let the bill land on money that has been waiting for it.

Below is one real list worked through to the dollar, the reason the first year costs more than the second, and a tracker you can copy tonight.

"Beware of little expenses; a small leak will sink a great ship." — Benjamin Franklin

💧 What are sinking funds, and how are they different from savings?

Sinking funds are pots of money you build up month by month for a cost you can already name and date. Savings, by contrast, are open-ended, and an emergency fund covers events you cannot predict.

The three get mixed up constantly, and the mix-up is the reason a registration bill still feels like an emergency in November.

• Sinking funds: known cost, known month, fixed monthly amount. Car registration in June is a sinking fund.
• Savings goals: a target with a flexible date, such as a house deposit. The savings planner guide covers how to run these.
• Emergency fund: money for what you cannot predict. The emergency fund spreadsheet guide explains how big it should be.

The name comes from business accounting, where a fund is deliberately sunk a little at a time to retire a debt or replace an asset. At home it just means paying for the dentist before the dentist sends the bill.

📋 What should be on your sinking funds list?

Your sinking funds list should hold every cost that arrives once or twice a year and is big enough to bend a normal month. Here is a worked list of eight, with the monthly amount each one needs.

The costs are an illustration I built for this guide, not a rule for what your life should cost. Swap in your own from last year's statements.

Sinking fund	Cost per year	Due	Set aside each month
Vet, dentist and glasses	$480	Apr	$40
Car registration and service	$960	Jun	$80
Holiday	$1,800	Jul	$150
Annual insurance	$540	Aug	$45
Back to school	$360	Aug	$30
Annual subscriptions	$240	Oct	$20
Birthdays	$300	Nov	$25
Christmas and gifts	$1,200	Dec	$100
Total	$5,880		$490

Eight costs worth $5,880 a year come to $490 a month. Every figure is the cost divided by 12, so car registration and service at $960 becomes $80 and the holiday at $1,800 becomes $150.

Look at where the money actually lands, though. Nothing is due until April, then July alone asks for $1,800.

That uneven calendar is the whole reason the system works. A lumpy year is hard to live through, and a flat $490 a month is easy.

If you are not sure what belongs on your own list, start with the big three: anything for the car, anything for the house, and anything that involves other people's birthdays. The travel budget spreadsheet guide covers the holiday fund in more detail.

🧮 How do you work out the monthly amount for a sinking fund?

You work out the monthly amount by dividing the cost by the number of months left until it is due. The formula is one line, and the only thing that changes it is when you start.

Take the Christmas fund. It costs $1,200, it is due in December, and here is what the monthly amount does as the months run out.

Start in January and you set aside $100 a month. Start in April and it is $133. Start in July and it is $200, and from October it is $400, four times the January figure for exactly the same gifts.

The total never changes. Only the number of months you have to spread it across does, which is why the best day to start a sinking fund is today.

Our free savings goal calculator does this division for any target and date, if you would rather not do it by hand.

⚠️ Why does the first year of sinking funds feel harder than the second?

The first year feels harder because every fund starts empty, so the early bills have far fewer months to fill. From the second year on, each fund refills after it pays out and the monthly amount settles down.

Here is the same list started cold on 1 January. Each fund has only as many months to fill as there are before its due date, so the vet fund has four months to find $480 and the car fund has six to find $960.

Sinking fund	Due	Steady year	Year one, starting in January
Vet, dentist and glasses	Apr	$40	$120
Car registration and service	Jun	$80	$160
Holiday	Jul	$150	$257
Annual insurance	Aug	$45	$68
Back to school	Aug	$30	$45
Annual subscriptions	Oct	$20	$24
Birthdays	Nov	$25	$27
Christmas and gifts	Dec	$100	$100
Total		$490	$801

Steady state is $490 a month. Year one, if you want every fund full on its due date, is $801 a month, which is $311 more. Put another way, if you start cold at $490 a month, the funds are $1,915 short when their bills arrive.

That gap catches a lot of people in the first spring, and they decide sinking funds do not work. They do. The first year just needs a plan, and any of these will do.

• Fund in due-date order. Fill the vet and car funds first and let the December funds start slowly, since they have the longest runway.
• Pay the early bills partly from the normal month. If a fund is short in April, cover the difference from the regular budget once, and fund it fully from then on.
• Use a windfall as the opening cushion. Pooled across all eight funds, a steady year needs $220 in the pot on 1 January and never dips below zero after that. A tax refund covers it.
• Trim the list in year one. Start with the three biggest costs and add the rest as each fund pays out and frees up cash.

If sinking funds feel like another fixed bill, the zero based budget guide shows where they sit in a month that is assigned to the last dollar.

🪣 How many sinking funds should you have, and where does the money live?

Most households do well with six to ten sinking funds, kept as separate lines in a spreadsheet and held together in one savings account.

Fewer than four usually means known costs are missing from the list. More than ten means you are maintaining the system instead of using it. Fold small costs together: gifts, birthdays and Christmas are often one fund, and so are annual subscriptions.

One account with a tracker beats ten accounts with no tracker. The sheet does the labelling, so the bank only has to hold the total.

The one habit worth copying from people who run this for years is the sweep. Move the money one day after payday, not at the end of the month. Money still sitting in the spending account three days after pay has mentally been spent, and it rarely makes it across.

If you prefer the feel of cash, the digital cash envelope tracker guide runs the same idea with envelope names instead of fund names.

📆 When do people go looking for sinking funds?

In our own shop, people go looking for a money system most in January, then again in December, which is when the biggest yearly bill of all arrives.

I checked our order exports. I counted 55,712 purchases of money-tool spreadsheets across 2024 and 2025, the only two full calendar years on record, and sorted them by month.

Month	Share of purchases	If months were equal
January	14.1%	8.3%
December	11.7%	8.3%
The other ten months, on average	7.4%	8.3%

December is the second busiest month at 11.7%, about 40% above an even share, and it sits behind only January. I cannot see why anyone buys when they do, so this is a pattern and not a proof, but it fits the picture: Christmas is the yearly cost almost everyone knows about and almost nobody funds.

The practical takeaway is the late-start ladder above. If December is when you notice, a Christmas fund started in October is $400 a month. Started in January it is $100.

📊 How do you track sinking funds in a spreadsheet?

You track sinking funds with one row per fund and five columns: name, target, due date, monthly amount and current balance, plus one cell at the top that adds up the monthly total.

Target and due date are fixed. The monthly amount is a formula, the target minus the balance divided by the months left, rounded up. Balance is the only column you touch on sweep day.

The top cell is the one that matters. It tells you the single number to transfer each pay cycle, and when a fund is added or a bill changes, that number updates itself.

Dates are the other half of the job, which is why a calendar helps. This is the bill calendar tab of the Ultimate Budget System, using its sample data, with yearly bills placed on the dates they fall due. Seeing the date next to the amount turns the abstract fund into a bill with a deadline.

🚧 Mistakes that quietly drain sinking funds

• Starting without a plan for year one. Fix it: fund in due-date order and cover the early bills partly from the normal month.
• Raiding a fund for something else. Fix it: if you must borrow, write the repayment into next month so the fund is whole before its bill.
• Forgetting to reset after the bill is paid. Fix it: reset the target and the next due date in the same week, or the following year arrives as a surprise.
• Using last year's cost forever. Fix it: check each fund at renewal and bump the target by what actually changed.
• Too many tiny funds. Fix it: fold anything under about $15 a month into a broader fund.
• Mixing them with the emergency fund. Fix it: keep them as separate lines so a predictable bill never eats your real safety net.

🎯 Your action steps this week

• Open last year's statements and list every cost that arrives once or twice a year.
• Write the amount and due month beside each one, using last year's figure if you do not have this year's.
• Divide each cost by the months left, and add them into one monthly transfer.
• Decide how you will handle year one: due-date order, a windfall, or trimming the list to the three biggest.
• Set a sweep day one day after payday and automate it if your bank allows. If you are also chasing a bigger goal, the savings challenge tracker guide shows how to run one alongside.

💬 Quick questions

What are sinking funds?

Sinking funds are small amounts you set aside every month for a cost you already know is coming, such as car registration, insurance or Christmas. Each one has a name, a due date and a monthly amount, so the bill is paid from money that is already waiting.

How do I work out how much to put in a sinking fund?

Divide the cost by the number of months until it is due. A $1,200 Christmas fund started in January is $100 a month. The same fund started in October is $400 a month, because there are only three months left to fill it.

Are sinking funds the same as an emergency fund?

No. Sinking funds cover costs you can name and date today. An emergency fund covers events you cannot predict. Keep them as separate pots so a predictable bill never drains the money meant for a real surprise.

How many sinking funds should I have?

Most households do well with six to ten. Fewer than four usually means you are missing known costs. More than ten adds upkeep that outweighs the benefit, so fold small costs into one fund such as gifts or annual subscriptions.

Where should I keep sinking fund money?

A separate savings account is the simplest option, with each fund tracked as its own line in a spreadsheet. Move the money soon after payday so it is out of the spending account before it feels available.

The envelope will still arrive on the doormat. With sinking funds, it just arrives on a day you have already planned for.

To your financial freedom,
Ren

This article is for general information only and is not financial advice. It does not take into account your personal situation, needs or objectives. Please consider speaking with a qualified financial adviser before making financial decisions.