You opened the joint account. Now you are both staring at the transfer screen, and neither of you knows what number to type.

So you guess. Rent plus a bit. It works until March, when the car insurance renews for the year and takes the account into overdraft on the same day as the energy bill.

Search for how much to put in joint account for bills and the pages that come back, mostly banks, say “list your shared expenses” and stop there. The list is the easy part. What goes wrong is the bills that don’t come every month, the paydays that don’t match the due dates, and having nothing spare. Here is the whole sum, worked through with one household’s numbers.

How much to put in joint account for bills: a year, divided by twelve

The mistake is adding up one month. Pick any month and it is missing something: the quarterly water bill, the car insurance that renews once a year, the registration, the home cover. Those are exactly the bills that empty a joint account, because nobody put money aside for them.

So add up twelve months and divide. Here is the example household in the diagram above. The numbers are illustrative; yours go in the same slots.

That comes to $3,080 a month. Notice the energy line. Use the average of the last twelve bills, never the summer one, or January will find you out.

Put every bill in once, at its own rhythm

The sum is only as good as the list, and the list lives in somebody’s head. In Chirpy, open Money, find Repeats and tap Add a repeat. Car insurance, 960, Every year, the renewal date. Water, 150, Every quarter. Rent, 1,800, Every month, the 1st.

Each one posts itself to the household ledger on its date and appears on the household calendar beforehand, on both your phones. The car insurance stops being a March surprise and becomes a line you both scrolled past in February. Chirpy Basic is free for the whole household, up to six people, no card, and Repeats are on it.

Ask is on every plan too. Type what bills are due before the 1st? and it reads your Repeats and answers with the list and the amounts, which is the question you are really asking every time you look at the joint balance.

Two buffers: one monthly, one only once

A joint account that holds exactly the bills will go overdrawn. Prices creep, a bill arrives two days early, somebody adds a streaming service and forgets to mention it.

Monthly headroom. Add about five per cent and round up to a figure you can remember. $3,080 plus five per cent is $3,234; round up and the transfer is $3,250. Whatever is left over just stays in the account and grows into the next buffer.

A starting cushion, once. Dividing the car insurance by twelve only works after twelve months of saving. If it renews next month, there is $80 put aside for a $960 bill. So seed the account, once, with the biggest lumpy bill on your list. After the first year the monthly share has caught up and the cushion is just a cushion.

A joint account goes overdrawn in the month a yearly bill lands, never in an ordinary one.

Want a separate pot for the yearly bills rather than one balance? Our guide to sinking funds for annual bills sets that up step by step.

Then split it, and only then

Couples tend to argue about the split first and the total second. Do it the other way round. Once the total is agreed, the split is a single multiplication.

The usual fair split is by take-home pay. In the example, one person brings home 60 per cent of the household’s income, so they put in $1,950 and their partner $1,300. If your incomes are close, halves are simpler and nobody minds. If they are far apart, read how to split bills unequal incomes, which works out what each method leaves each of you to live on.

• Use take-home, not salary. Pension and tax come out before either of you sees the money.
• Agree it in writing. A note in the household notes is enough. In eight months nobody will remember whether the gym was in.

When paydays don’t line up with the bills

Set each transfer for the day after that person is paid, and make sure both land before the biggest bill. If rent leaves on the 1st and one of you is paid on the 28th, the 29th works. If one of you is paid on the 15th, either move the rent date or carry a month’s share in the account from the start.

Paid every two weeks

Twenty-six paydays a year do not divide into twelve months. Take the monthly share, multiply by twelve, divide by twenty-six. In the example that is $1,300 times twelve, divided by twenty-six: $600 every other Friday. Two months a year have three paydays, and those two extra transfers quietly top up the cushion.

One thing your bank does better: its app shows the joint account’s real balance to the cent, and Chirpy never connects to banks, so it cannot. What the bank shows is what has already gone. Chirpy shows what leaves next, by date, with each bill on the calendar you both open for everything else.

What goes in the joint account, and what stays out

Anything you both use goes in: housing, energy, internet, insurance, food, the car if it is shared, childcare. Personal spending stays out, and so do gifts for each other, for obvious reasons.

Food is the line that drifts, because it is the one bill you choose every week. In Chirpy, set a groceries budget of the same figure you put in the sum, $760 here. Every shop either of you logs fills the same bar, so the second person to go shopping can see what the first one spent. For the budget around it, our guide to the household budget couples actually keep using covers the rest.

Redo the sum when a bill changes

The figure goes stale the moment a renewal letter arrives with a bigger number on it. When that happens, edit the Repeat in Chirpy, change the one amount, and redo the sum. If it moves the monthly figure by more than the headroom, change the transfers.

Otherwise, look twice a year. Put the review on the household calendar so it belongs to the house, not to whichever of you remembers things. Fifteen minutes, one number, and the account stops surprising you.

Common questions