Sinking funds for ADHD: never get ambushed by a bill you knew was coming

Car insurance renews in March. You knew that in March last year. You will be surprised by it in March this year.

That is not forgetfulness in the ordinary sense. It is how an ADHD brain handles time: things are either now or not now, and "in eleven months" is as far away as "never". The bill is not forgotten so much as filed under not now until the morning it becomes now and the budget breaks.

Sinking funds are the fix. One calculation, one payday habit, and the ambush stops.

What a sinking fund actually is

A sinking fund is money set aside a little at a time for a specific cost you know is coming. Car insurance is $900 a year, so you put $75 aside each month. When March arrives, the $900 is sitting there. The bill is paid from money that was always meant for it, and your normal month is untouched.

That is the whole idea. It is not saving, exactly; it is pre-paying yourself for a bill in slow motion.

Why it works so well for ADHD brains specifically

• It moves the decision to payday. You do not have to remember March in March. You made the decision once, and the money moves every payday without thought.
• It turns a lump into a flat line. ADHD budgets die on spikes. Sinking funds remove the spikes.
• It makes "future you" concrete. The pot has a name and a number. "Car insurance: $525 of $900" is visible; "I should save for insurance" is not.
• It kills the guilt. The most common ADHD money story is "I was doing fine and then one bill wiped me out and I gave up". Sinking funds make that story impossible.

The bills that belong in a sinking fund

Anything that arrives less often than monthly. The usual suspects:

• Car: insurance, tax or registration, inspection, servicing, tyres
• Home: insurance, boiler service, annual repairs allowance
• Health: dentist, optician, glasses or contacts, vet
• Tech: annual subscriptions, software renewals, domains, phone replacement
• Family: school costs, uniforms, trips, kids' activities by term
• Gifts: birthdays (count them), Christmas or Eid, weddings
• Travel: the holiday you take every year
• Life admin: passport, licence renewals, professional fees

If you are reading this thinking "I forgot about at least four of those", that is the point.

Set them up in twenty minutes

Step 1: List every irregular bill

Go through last year's bank statements or emails for anything annual, quarterly or one-off-but-recurring. Write down the name, the amount and the month it lands.

Step 2: Add up the year

Total every line. For a typical household it is somewhere between $2,000 and $6,000 a year. This is the number that has been "randomly" breaking your budget.

Step 3: Divide by twelve

That is your monthly sinking fund contribution. $3,600 a year becomes $300 a month. If you are paid biweekly, divide by 26 instead.

Step 4: Decide where the money lives

Two good options. One separate savings account called Known bills that you never touch for anything else, or one pot inside your budgeting tool that shows the balance. The bad option is leaving it in your main account "mentally set aside". Mental set-asides do not survive a Saturday.

Step 5: Automate the transfer for payday morning

Before you see the money. This is the one automation every ADHD budget needs. If it has to be done by hand, it will be done for two months.

One pot or many?

Personal finance blogs love separate pots for everything: a car pot, a gift pot, a holiday pot. For ADHD brains this often backfires, because ten pots means ten balances to track and ten small transfers to set up.

Start with one pot for all known bills. One number in, one number out. Only split it if you find yourself raiding the holiday money for the dentist and resenting it. Even then, three pots is plenty: Car and home, People and gifts, Everything else.

The ADHD Budget Planner uses the one-pot approach: you enter each yearly bill once, it works out the monthly share, and a single Known bills bar fills up while the list underneath shows what it covers and when.

What to do when the bill arrives

Pay it from the pot. Then do nothing else. Do not "top the pot back up" or feel that the balance dropping means something went wrong. The balance dropping in March is the pot doing its job.

The pot is designed to go up and down through the year. What matters is the yearly total and the monthly contribution, not the balance on any given day.

The first year is lumpy; that is fine

If you start in September and car insurance is due in October, the pot will not have $900 in it. You have two choices: pay the shortfall from Fun or Savings this once, or add a temporary extra contribution for a few months until the pot catches up. Either is fine. By the second year, every bill is fully funded before it lands, and the ambush never happens again.

Sinking funds and the rest of your budget

Sinking funds are the Known bills box in the six-box budget, and the fourth bucket we add to the 50/30/20 rule. If you already run either, this post just fills in the detail.

Want the maths and the tracking done for you? In the ADHD Budget Planner, you type each yearly bill once and it calculates the monthly share, shows the Known bills pot filling up, and lists what is due in which month so nothing moves back into not now. Phone, tablet and computer, offline, data on your device. One payment, no subscription, delivered by email straight after checkout. See the demo.

FAQ

What is the difference between a sinking fund and an emergency fund?

A sinking fund is for costs you know are coming (insurance in March). An emergency fund is for costs you do not (the boiler dies in January). Both matter; the sinking fund is the one most budgets are missing. See the visual emergency fund tracker.

How much should I put in sinking funds?

Exactly the yearly total of your irregular bills divided by twelve. It is not a target you choose; it is a number you calculate.

Should sinking funds be in a separate bank account?

Ideally yes, or in a budgeting tool that shows the pot separately. The only rule is that it must not look like spendable money in your main account.

What if I have too many irregular bills to fund them all?

Fund the unavoidable ones first (insurance, tax, essential renewals) and let gifts and holidays be smaller for a year. A partly funded pot beats an unfunded one every time.

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