Deposit-insurance allocation check

The check is deliberately plain arithmetic on three numbers: a deposit total, a count of institutions treated as separately insured, and a per-institution limit typed in by the reader. It embeds no scheme’s rulebook, no country’s table and no current figure — the line it tests against is exactly the one supplied, which is what keeps a signed calculator from quietly impersonating a regulator.

The two outputs are two different readings of the same line. The minimum-institutions figure divides the total by the limit and rounds up: the smallest count under which full coverage is arithmetically possible at all. The shortfall figure takes the count actually supplied, splits the total evenly, and reports how far each equal slice sits above the limit — with nothing exposed reported as exactly that, rather than as a rounding accident.

Even splitting is the assumption doing the most work. Real balances are lumpy — a matured certificate here, a current account there — and an uneven spread can leave one institution exposed while the average looks fine. What the check describes is the best-behaved arrangement of the count it was given; matching reality to that arrangement is the reader’s side of the bargain, and no output here claims it has happened.

Coverage in the world is richer than one number per institution: schemes recognise ownership categories, joint holdings and temporary balances differently, and their aggregation rules decide what “separately insured” even means. None of that is modelled, and the page does not read any scheme’s terms. The arithmetic sizes the problem; what protection actually applies is for the governing scheme’s own published rules to say.

The most important design decision in this calculation is a refusal. The coverage limit is an input, not a constant: no scheme’s rulebook is embedded, no country’s table is shipped, and no current figure is asserted anywhere in the engine or on this page. The line tested against is exactly the one supplied — which is what keeps a signed calculator from quietly impersonating a regulator.

The reasons are practical as well as principled. Schemes differ by country in what they cover, in how much, and in how they aggregate accounts; their figures are revised, sometimes at short notice and sometimes temporarily; and a reader’s deposits may sit under a scheme entirely different from the one a default would have assumed. A hard-coded number would be right for some readers, stale for others, and wrong for the rest — and all three would look identical on screen.

So the workspace ships an illustrative default and labels it as illustrative, and the figure that governs any real balance is whatever the scheme in question currently publishes. Looking that up — from the scheme itself rather than from a summary of it — is the one step of this exercise that cannot be automated, and it is the step that decides whether the outputs mean anything.

The calculation returns two figures, and they answer different questions. The first divides the total by the limit and rounds up: the minimum count of separately insured institutions under which every part of the total could sit within the line. It describes the best case and takes no view on whether the reader’s actual arrangement resembles it.

The second takes the count of institutions actually supplied, splits the total evenly across them, and reports how far each slice sits above the limit. This is the reading about the present arrangement rather than an ideal one, and it collapses to nothing — reported as exactly nothing — the moment the even slice drops under the line.

Read together, the two say something a single figure could not. When the shortfall is anything but nothing, the minimum count is the size of the fix, and the distance between that count and the count in use is how far the present arrangement stands from the smallest workable one. Raising the institution count by one in the try-it below and watching the shortfall vanish at exactly the count the first output had already named is the fastest way to see that the two figures are describing one line from two sides.

Real balances are lumpy. A matured certificate lands in one place, a current account carries the month’s salary in another, an old savings account holds whatever was left in it years ago. The even split this calculation assumes is the best-behaved arrangement of the institutions it was given — and an uneven spread can leave one institution well above the line while the average looks entirely comfortable.

That gap between the modelled split and the actual one is the reader’s side of the bargain, and no output here claims it has been closed. The arithmetic sizes the problem and says whether a fit exists at all; where the money actually sits, and whether the institutions counted are genuinely separately insured under the governing scheme, are facts it cannot check. When two entities might share a licence, running the check at the smaller count is the honest move — the pessimistic reading is the one that does not need to be right about the licence.

The other moving part is time. Interest keeps arriving after the check is run, so a total that fits under the line today drifts over it later, entirely on its own. The pace of that drift is what the earlier lessons in this journey measured, which is why this is a check to repeat on a schedule rather than to pass once — and why a total rounded upward before entering it costs nothing and biases the answer in the safer direction.

Coverage in the world is richer than one number per institution. Schemes recognise ownership categories, joint holdings, trust arrangements and temporary high balances differently; some protect certain account types and not others; their aggregation rules decide what “separately insured” even means, and those rules are where most real cases are actually decided. None of that is modelled here, and this page does not read any scheme’s terms.

What remains is deliberately narrow and genuinely useful: three numbers in, two numbers out, and a vague unease turned into a count of institutions and an exposed amount per slice. That is a good beginning to a conversation with the institutions involved or with a professional adviser, and a poor substitute for either. This page is an educational reference; it makes no statement about any scheme’s rules and no recommendation about where anybody should hold money.

The engine below arrives pre-filled with the pack’s own declared example: a total in the middle six figures sitting across two institutions, tested against an illustrative per-institution limit. Replace that limit with the figure the scheme governing your own deposits currently publishes before reading anything into the outputs — every number on screen is an answer about the line you supplied. Then raise the institution count by one and watch the shortfall collapse at exactly the count the first output had already named.

Read the minimum-institutions figure as what full coverage would take in the best case, and the shortfall as what an even split leaves above the line at each institution today. Neither is a statement about what any scheme actually protects. Both are computed live by the verified engine from your inputs; this page stores neither.