Where Supplier Documents Are Stored

Suppliers often embed their own PDF of the invoice inside the electronic document. Those files are copied onto the purchase document Business Central creates, through Business Central's standard Document Attachment framework — not a table of this app's own. That choice is what lets them follow whatever storage you have configured, including external file storage.

The Supplier Document box on the purchase document previews the first page, and Open Document downloads the file.

Why the standard framework

Anything stored in a table of the app's own would sit outside Business Central's storage options and count against the tenant's database capacity — files and blob data in the database, including the Tenant Media and Tenant Media Thumbnails tables, count towards that quota.

By going through Document Attachment, a customer who points attachments at Azure Blob Storage, an Azure File Share or SharePoint keeps supplier PDFs out of the database entirely, with no change to this app.

Set up external storage

External file storage is standard Business Central, generally available from 2026 release wave 1. You need it only if you want attachments out of the database — the app works either way.

Create the file account:

Choose the Search icon, enter External File Accounts, and then choose the related link.
Choose Add a file account to start the setup guide.
Pick Azure Blob Storage, Azure File Share or SharePoint, and choose Next.
Fill in the connection details for that storage type — for Azure Blob Storage that is the storage account name, the authorization type (SAS token or account key), the secret, and the container name.
Choose Next, review, and choose Finish.

Point document attachments at it:

Choose the Search icon, enter File Scenario Assignment, and then choose the related link.
Choose Assign scenarios, select your file account, and choose OK.
Select the account line, choose Assign Scenarios, and select the Document Attachments - External Storage scenario.
On the External Storage Setup page that opens, turn on Enabled and accept the warning.
Set the Root folder. Business Central organizes subfolders under it by environment, company and table.
Decide whether to turn on Delete External File on Attachment Delete.

Only attachments added after you enable this go to external storage. To move the ones you already have, use the Storage Sync action on File Scenarios or External Storage Setup, which also moves files back into the database if you decide to stop.

One thing to be clear about before you switch it on: files in external storage are yours to back up. Microsoft does not back them up as part of your Business Central environment, and a file deleted there is gone from Business Central too.

The preview needs the copy in the database

This is the one behavior worth knowing before somebody reports it as a bug.

Open Document always works, whatever your storage. It goes through the same routines Business Central's own implementation uses, which external file storage hooks into.

The preview only draws from the copy in the database. If the file has been removed from internal storage and lives only in your external container, the box falls back to a placeholder even though the file is perfectly safe and downloadable.

Measured on a real environment rather than assumed: with the database copy present the preview drew page 1; after the internal copy was removed — file still in the Azure container, still marked as stored externally — it fell back to the placeholder; after copying it back from external to internal, it drew again.

The message you get is:

Business Central cannot reach the contents of this attachment. If document attachments are kept in external storage, the file may be missing there. Choose Open Document to try downloading it.

So: a blank preview with a working Open Document is a preview limitation, not a lost file. Use the Storage Sync action on File Scenarios or External Storage Setup to move files between internal and external storage if you want previews back.

When an attachment is not copied

The Supplier Attachments column on Incoming Supplier Recognition records what happened to each one, including the cases where nothing was copied:

The supplier sent no attachment.
The attachment carried no content, or was not valid base64.
The attachment was larger than the size limit, so it was left in the e-document instead of copied onto the invoice.
The document itself could not be read back, so no attachment could be looked for.

Nothing is dropped in silence. A file that was too large is named, and the original is still inside the e-document.

Other formats