What a stranger would need to know
If you were in hospital for a week, could anyone else keep your life running? The answer is usually no, and the fix takes one evening.
This is the least pleasant piece of household admin and the one with the highest return. Not a will — something far more ordinary. If you were unexpectedly out of action for two weeks, what would simply stop?
For most people the honest answer includes: a direct debit nobody else knows about, a service that renews, a plant, a key, a person expecting something on Thursday. None of it is catastrophic. All of it is unnecessary.
The one page
Write a single page a competent stranger could follow. Not your passwords — the map.
What leaves the account automatically, and roughly when. Who to tell within the first two days — work, school, one or two others. What is in the house that needs doing: a pet, a plant, a boiler that does a thing. Where the important documents are. Which bills come to paper and which to email.
One page. If it takes three, it is a filing system, and nobody reads a filing system during a crisis.
Then tell one person where it is
The page is worthless if it is in a locked space only you can open. One other person needs to know it exists and how to get to it. That conversation takes two minutes and is the entire point of the exercise.
For medical specifics — conditions, medications, allergies, who to call — the same principle holds and the stakes are higher: this is the one case where the information is useless unless somebody else can reach it quickly.
Why this is worth an evening
Because the cost is wildly asymmetric. An evening now against a week of somebody guessing — or worse, a week where nobody can guess, and the small things quietly compound into large ones.
And because writing it is the fastest audit of your own arrangements you will ever do. Most people find two or three things on that page that should not have existed at all.