Your bank balance is not your budget

Open your banking app. It shows a number. It is correct, it is up to date, and it is the wrong number to make a decision with.

Not because the bank is hiding anything. Because that number answers a question nobody actually has. It tells you how much money is in the account. It does not tell you how much of it is still yours to decide about — and those are different amounts, usually by a lot.

The balance is a sum of things that have nothing to do with each other

Whatever your bank shows right now contains, mixed together and indistinguishable:

Money that is already spent but not yet debited. The rent leaving on the 1st. The direct debits. The card payment from Saturday that has not settled.
Money that belongs to a future month. The €900 sitting there because an insurance bill lands in March — and if you have been building a cushion, the part of the balance that is next month’s, not this month’s.
Money that is genuinely free, which is what you wanted to know, and which is the only part the number does not show you separately.

A balance of €2,340 can be €60 of freedom. It can also be €2,340 of freedom. The balance is identical in both cases, which is the entire problem: the number does not vary with the thing you are trying to decide.

What happens when you spend against it anyway

This is not a lecture about discipline. There is a measured effect, and it runs in the direction you would not want.

Morewedge, Holtzman and Epley ran four experiments on what they called the accessible account effect. When a large resource account is the one you happen to have in mind, each unit of consumption feels smaller, and people consume more. When a small account is in mind, the same purchase feels bigger and people consume less. They found it with money, and also with calories and with time — the effect is about which pot is mentally accessible, not about money specifically.

Your bank balance is, structurally, the largest accessible account you own. It is on the first screen of the app, it aggregates everything, and it is the number you see every time you check anything. A €14 lunch measured against €2,340 is a rounding error. Measured against the €60 you actually have left, it is a quarter of it. Same lunch, same finances, different denominator.

The complementary result is just as useful. Soman and Cheema studied earmarking and partitioning among low-income households and found that people save more when earmarked money is split across separate accounts than when it is pooled into one, and that a visual reminder of what the money is for raised saving further.

Put the two together and you have the whole argument for envelopes, stated in the negative and the positive: one big pooled number makes you spend more; the same money partitioned and labelled makes you save more. Neither result is about wanting it enough.

What that produces, at national scale

France measures this, and the figure is unusually vivid.

In the 2025 edition of the lesfurets/CSA Research barometer — an online survey of a nationally representative sample of 1,007 people aged 18 and over, fielded 18–20 November 2025 — 24% say they are overdrawn every month or almost every month, and, on average, the balance goes negative from the 18th of the month. Among 25–34 year-olds the monthly figure reaches 42%.

Two honest notes: it is a declarative survey, not bank records, so it measures what people report; and it describes France, not Europe. But the shape is the point. A month has thirty days, and the number people steer by runs out on the 18th. That is not a discipline failure distributed across a quarter of a country. That is a measurement that stops being informative two-thirds of the way through the period it is supposed to cover.

The number that answers the question

An envelope budget replaces the balance with a decomposition. Not an estimate of it — a decomposition, meaning the parts add back up exactly:

To assign + the sum of all envelope balances = the cash in your budget accounts

The identity is not a display convention. Both of these cases are covered by tests, because both once produced a number that was too big.

To assign is what has arrived and has not yet been given a job: income received, minus everything assigned to envelopes, minus overspends from earlier months that were never covered. When it reads zero, every euro in your accounts has a name. When it reads €60, that is the sentence “I can decide about €60”, which is what you opened the app to find out.

Two details in that definition are worth pulling out, because they are exactly where the identity would quietly stop being true.

Money you moved out of the budget stops counting. Transfer €400 to a savings account you keep off-budget and the on-budget side of that transfer reduces what you have to assign — the cash genuinely left. Treating every transfer as internal and neutral would leave you assigning €400 that is no longer there.

An overspend nobody covered is subtracted. If an envelope ended a past month at −€300 and the balance was reset rather than carried, the screen forgets it, but the €300 left your account for real. It comes off To assign, or the budget would be describing money that has been spent.

Neither case is exotic — the first is “I moved some money to savings”, the second is “I went over on groceries in June and never dealt with it”. Both once made the number too big, and both now have a test.

What the balance is still good for

It is not a bad number. It is a bad budget.

It is the right number for exactly one question: will this payment go through today? For that, nothing else will do — envelope balances do not stop a direct debit from bouncing. Keep an eye on it for solvency, and stop asking it what you can afford. Those are two jobs and it can only do one.

What this will not fix

A decomposition does not change the total. If the honest answer is €60, seeing €60 will not feel better than seeing €2,340. It will just be true earlier — which is the only advantage on offer, and it is worth more on the 12th than on the 28th.

And it depends on the accounts being right. The identity holds against the cash your budget knows about. An account you never added, or one you added but excluded, is outside it. The number is exact about what it covers and silent about what it does not.

The bank is answering a question about itself: how much of your money are we holding? You are asking a question about your month. The two have the same units and nothing else in common.