How to send confidential documents

Send a link rather than an attachment, give it an expiry, put a password on it, and send that password through a different channel. Those four steps take about a minute and prevent nearly every realistic way a confidential document leaks. Encryption is necessary but it is not the control that saves you — a link that still works in two years is far more likely to be the problem.

Why not an attachment

An emailed attachment is permanent and untraceable. It sits in the recipient's mailbox indefinitely, it gets forwarded without your knowledge, it is backed up by systems you cannot see, and if you sent it to the wrong address there is nothing you can do.

A link can be revoked, expired and limited. For anything confidential that is the whole argument, and it holds regardless of file size.

The four steps

1. Upload and send a link. Any reputable service. The email itself stays tiny, which also means it will not bounce off a strict mail server.

2. Set an expiry. The shortest that is practical. For a contract someone needs to read and sign, a week. The point is that the link stops being a live credential once its job is done.

3. Add a password. This is what protects you if the email is forwarded or the mailbox is compromised.

4. Send the password separately. By text, or say it on a call. A password in the same email as the link protects against nothing — if someone can read one, they can read the other. This is the step people skip, and skipping it makes step three decorative.

What else to check

Can you revoke it? Ask your service specifically. People assume this exists and it often does not. It is what turns "I sent that to the wrong person" from an incident into an inconvenience.

Can you limit downloads? A one-time link suits a single sensitive document well. It also gives you a signal: if the link was already used when your recipient tries it, you have learned something you needed to know.

Do you know when it was downloaded? For a contract or a legal document, being able to say when the other side received it is occasionally worth a great deal.

Confidential versus personal data

These attract different obligations and it is worth knowing which you are dealing with.

Confidential is a duty you owe — under a contract, an NDA, professional rules, or simple commercial sense. Breaching it is a contractual or professional problem.

Personal data is information about identifiable people, and it is regulated whether or not anyone asked you to keep it confidential. That brings legal obligations: a lawful basis, a processing agreement with whoever stores it, retention limits, and breach notification duties.

A commercial contract is confidential. An employee file is both. A client's customer list is both, and the second is the one with statutory consequences. What the GDPR actually requires covers that side, and sending sensitive client data covers the sharper special-category cases.

Where encryption fits

Every serious service encrypts in transit and at rest. The question worth asking is who holds the key.

If the service holds it — which is the normal design — the service can technically read your file, and so can anyone who lawfully compels them. That is usually an acceptable trade, and it is what makes previews and virus scanning possible.

If only you hold it, the service cannot read the file at all. Stronger, and it costs you features and forgiveness: lose the key and the document is gone.

The quickest test of which you have been sold: can the service show you a preview of the document, or recover your files if you forget your password? Either means it holds the key. The longer version.

For most confidential business documents, provider-held keys plus good access control is the right answer. Reach for the stronger property when the provider itself is part of what you are worried about.

Where the documents end up

Two things that matter more than they sound:

Which country's courts can compel the provider? That follows the company, not the data centre. A US provider storing data in the EU is still subject to US legal process. For documents under legal or professional privilege, this is not a theoretical concern. The explanation.

How long do they keep it after you delete it? Backups persist. Ask.

The habits

Send the minimum. Redact what does not need to travel. A page you did not send cannot leak.

Never reuse a link across recipients. You lose the ability to say who has what.

Check what you actually shared by opening your own link in a signed-out browser once. This catches over-sharing and it catches broken access, which are the two most embarrassing outcomes.

Review old shares. Most people have live links from years ago they have entirely forgotten. That audit is worth more than any product decision on this page.

For the general version of this, without the confidentiality framing, see how to send large files securely. For comparing services on these properties, the secure services page.