I lost a wallet on a trip several years ago and spent two days reconstructing enough documentation to function. The preparation I adopted afterwards has since resolved four unrelated problems, none of which was a lost wallet.
What actually goes in it
A folder, held in three places, containing photographs or scans of the following.
Passport identification page, and any visa pages that are current.
Driving licence, both sides.
Travel insurance policy document, with the policy number and the emergency assistance telephone number clearly visible.
Payment cards, front and back, which sounds risky and is addressed below.
All booking confirmations — flights, accommodation, transport, activities — with reference numbers.
Prescriptions for any medication carried, with the generic names rather than brand names.
Vaccination records where relevant.
And a single page of emergency contacts, including somebody at home who can act on your behalf.
Where the three copies live
The part that matters, since one copy is not a system.
One in cloud storage, accessible from any device with a connection and a login.
One stored offline on the phone, since the cloud copy is useless without connectivity and connectivity is frequently the problem.
And one printed, in a bag separate from the one carrying the originals.
The printed copy is the one people skip and it has been the one that worked for me twice, because the situations where documents matter are frequently situations where a phone is also unavailable.
The card photograph question
Since photographing payment cards is obviously a risk.
The purpose is having the number to report a loss and the bank's telephone number, which is printed on the reverse and which nobody remembers.
The reasonable approach is to store this in an encrypted note or a password manager rather than in a photo library, and to include the reporting number rather than the full card details if that is sufficient.
The bank's international number specifically, since the freephone number printed on the card frequently does not work from abroad, which is a detail people discover at the worst moment.
What it has actually solved
The four occasions, since they were not the ones I prepared for.
A hotel that had no record of a booking, resolved by producing the confirmation with the reference number.
An immigration officer requesting proof of onward travel, which I had not thought to keep accessible.
A pharmacy abroad needing the generic name of a medication, which was on the prescription copy and which I could not have recalled.
And a car hire desk disputing the terms of a booking, resolved by the confirmation showing what had been agreed.
None was a lost document. All were situations where having the information immediately available converted a problem into a two minute conversation.
The onward travel point
Worth expanding since it catches people regularly.
Several countries require evidence of onward or return travel as a condition of entry, and airlines check this at departure because they bear the cost of returning anybody refused.
Enforcement is inconsistent, which is why many travellers never encounter it and those who do are unprepared.
Having the return booking accessible offline removes the entire category of problem.
The person at home
The element that is genuinely worth arranging.
Somebody who has access to the same folder, knows your itinerary, and can act — contact an insurer, send funds, speak to an embassy — is more useful than any document.
Sharing the folder with one trusted person before departure takes a minute.
It also addresses the situation nobody plans for, which is being incapacitated rather than merely inconvenienced.
The annual maintenance
The reason systems like this fail.
Documents expire, cards are reissued, policies renew, and a folder assembled three years ago contains a passport that has since been replaced.
Reviewing it before each significant trip takes five minutes and is the step that keeps it useful rather than reassuring.
What not to include
Worth stating since the folder is a security exposure in itself.
Full card numbers with security codes, which enable transactions rather than merely reporting a loss.
Passwords, which belong in a password manager rather than in a document folder.
And anything you would not want read by somebody who obtained access to the storage account.
The folder should contain what is needed to prove identity and to contact the right people, which is a narrower set than everything you carry.
Two-factor authentication on the storage account is the minimum protection given what is in it.
Passport validity
The requirement that ends trips before they start.
Many countries require a passport to remain valid for a period beyond the intended departure, commonly six months, and airlines enforce this at check-in because they bear the cost of a refused entry.
Blank pages are also required by some countries, in specific numbers.
Both are checkable against the destination's official requirements and are the sort of thing people discover at a check-in desk.
Noting the expiry date in the folder, and checking it against the destination's rule, takes a minute and prevents the most avoidable failure in international travel.