When a company first implements Microsoft Dynamics 365 Business Central, document storage is rarely the first topic people want to discuss.

The team is usually focused on more immediate questions. Can we migrate our opening balances correctly? Will the purchasing process work? How quickly can we start invoicing customers? Who needs which role and permissions?

Then the system goes live.

Before long, users begin attaching documents to almost everything: supplier invoices, customer purchase orders, signed delivery notes, product images, receipts, contracts, inspection certificates and scanned paperwork.

That is exactly what the attachment feature is designed for. The problem is that these files can gradually consume a meaningful amount of database capacity, particularly in a document-heavy business.

Microsoft now gives Business Central customers another option. Document attachments can be stored outside the Business Central database in external file storage, while users continue accessing them from inside Business Central. Supported options include Azure Blob Storage, Azure File Share and SharePoint document libraries. Partners and developers can also extend the framework to support other providers.

It sounds like a small architectural change, but for the right organisation, it can make a noticeable difference.

First, what exactly is changing?

Think of Business Central as the place where your business transaction lives.

A purchase invoice, for example, contains the supplier, invoice number, posting date, amount, dimensions and approval status. A user might also attach the supplier’s original PDF invoice to that transaction.

Normally, the attachment is stored in the Business Central database. With external storage enabled, the transaction and attachment information remain available in Business Central, but the physical PDF, image or scanned document is stored in the external service you have connected.

From the user’s perspective, very little changes.

People can continue working from the Attachments FactBox or the Document Attachments page. They can attach, open, download and delete documents through the familiar Business Central experience. Behind the scenes, Business Central sends new files to the configured external storage and retrieves them when a user needs them.

That separation is the important part. Your ERP continues managing the business context, while a service designed for file storage looks after the files.

Why should a growing business care?

Imagine a distribution company that processes hundreds of supplier and customer documents every week.

The accounts payable team attaches vendor invoices. The sales team stores customer purchase orders. The warehouse adds proof of delivery documents. Procurement includes quotations and product specifications. Some of these documents are small, but others are high-resolution scans or images.

No single attachment looks like a problem. The pressure becomes visible only after thousands of files have accumulated.

Business Central tenants have limited database capacity. Microsoft’s documentation gives an example of 80 GB by default across production and sandbox environments, with additional storage provided per licence. Moving attachments outside the database can therefore help a company stay within its available capacity and potentially avoid purchasing additional database space.

A smaller database may also improve general system performance and reduce backup and restoration times. External cloud storage can be more cost-effective for large quantities of files and may provide useful capabilities for content management, sharing and long-term archiving.

The question I would ask is simple: Are you using valuable ERP database capacity to store information that is really just a file?

For many growing businesses, separating the two makes good operational and financial sense.

Which external storage services can you use?

Business Central supports three external storage options out of the box:

·       Azure Blob Storage

·       Azure File Share

·       SharePoint document libraries

The right choice depends on your organisation’s architecture, governance requirements and existing Microsoft investments.

Azure Blob Storage may be attractive when the priority is scalable cloud storage for a large volume of attachments. Azure File Share offers a file-share-based approach. SharePoint can be appealing to organisations already using Microsoft 365 for document management and collaboration.

This should not be treated as a one-size-fits-all decision. An organisation with a dedicated Azure team may have different preferences from a company whose document governance is centred on SharePoint.

My practical advice is to avoid choosing purely on the basis of price. Consider who will administer the storage, how access will be controlled, how backups will work and whether employees need to work with the files outside Business Central.

You can configure more than one external file account in Business Central. The External File Storage framework is also extensible, which means a partner or developer can add support for other providers, such as SFTP or OneDrive, through an extension if the standard services do not meet the requirement.

What does the setup involve?

The process has two main parts.

First, an administrator creates an external file account in Business Central. Using Tell Me, they search for External File Accounts, choose Add a file account, select the storage type and provide the required connection information.

For Azure Blob Storage, the configuration includes the Azure storage account, authorisation method, secret and container name. Azure File Share similarly requires the storage account, authentication information and file share name.

A SharePoint connection requires information from a Microsoft Entra ID app registration, including the tenant ID, client ID and client secret. The administrator also specifies the SharePoint location and a base relative folder path, such as Shared Documents/Attachments.

The second part is assigning the document attachment scenario to that account.

The administrator opens File Scenario Assignment, assigns the relevant file account and selects Document Attachments - External Storage. On the External Storage Setup page, they enable the scenario and choose an existing root folder or container.

Business Central then creates an organised folder structure underneath that root location. The hierarchy considers details such as the environment, company and source table. Attachments connected to sales documents, for example, can be grouped under a folder for the Sales Header table.

This structure matters because it prevents external storage from becoming one enormous folder filled with unrelated documents.

What happens to existing attachments?

Enabling external storage does not automatically relocate every file already held in your Business Central database.

By default, attachments added after the feature is enabled are stored externally. Existing attachments remain where they are until they are moved. The Storage Sync action, available from the File Scenarios or External Storage Setup pages, can be used to transfer existing files between the Business Central database and external storage.

The same capability is useful if an organisation later decides to stop using external storage. Files can be moved back into the Business Central database before the scenario is disabled.

This is an area where I would recommend planning rather than experimenting in a production environment. Decide which documents need to move, validate the destination and include testing in the implementation plan.

How many attachments are already in your current ERP or file system? That answer can help determine whether migration should be part of the initial Business Central project or handled as a separate activity.

What will employees notice?

Ideally, almost nothing.

A sales administrator can still drag a customer purchase order onto the Attachments FactBox of a sales order. An accounts payable clerk can still associate a PDF invoice with the relevant document. When someone chooses Open or Download, Business Central fetches the file from external storage automatically.

Business Central also appends a unique ID to the stored filename. This prevents two files with an identical name, such as invoice.pdf, from overwriting each other in the external location. The user continues to see the original filename in Business Central, while the externally stored version includes the unique identifier.

That is the type of behind-the-scenes detail I appreciate in a business application. Users should not need to understand the storage architecture just to open an invoice.

The responsibility that moves to your organisation

External storage is not simply a switch that reduces the Business Central database and leaves every other responsibility unchanged.

Once an attachment is stored externally, Microsoft does not back up or manage that file as part of the Business Central environment. Your organisation, or the administrator managing the external service, becomes responsible for backups, access controls and the continued availability of the files. If a document is deleted from external storage, Business Central can no longer retrieve it.

That distinction needs to be clearly understood before implementation.

The setup includes a Delete External File on Attachment Delete option. When it is enabled, deleting an attachment in Business Central also sends a request to remove the corresponding external file. When it is disabled, Business Central removes the attachment link, but the physical file remains in external storage until it is deleted separately.

Neither choice is automatically correct. Your decision should reflect the organisation’s retention requirements, privacy obligations and document management policies.

Do not overlook company copies and restored environments

External attachments also require attention when copying companies or restoring environments.

Business Central might copy the attachment metadata, but the externally stored files are not automatically duplicated. The copied records may continue pointing to the original storage location unless the files are migrated. The Migrate Files action on the External Storage Setup page can move attachments from a previous environment or company folder into the current external storage folder.

Administrators can also use the Storage Browser from the External File Accounts page to examine connected storage. Depending on the storage, it can display folders and files and provide actions to upload, download, delete or create folders. This can help verify that attachments are being stored as expected.

These may sound like technical details, but they matter during testing, upgrades, disaster recovery and environment refreshes.

A sensible conversation to have before go-live

External attachment storage will not be necessary for every new Business Central customer.

A smaller company with few attachments may be comfortable keeping everything in the Business Central database. A document-intensive organisation, however, may benefit from including external storage in its solution design from the beginning.

Before enabling it, I would bring finance, IT, compliance and the implementation partner into the same conversation. Discuss the expected attachment volume, preferred storage provider, security model, backup process, retention requirements and responsibility for ongoing administration.

Most importantly, agree on what happens when something goes wrong.

Who investigates if a file cannot be opened? Who monitors the storage service? Who restores an accidentally deleted document? Who reviews the application credentials used for the connection?

External storage can simplify database management, but only when ownership is just as clear as the technology.

Final thoughts

Storing attachments externally is a good example of a Business Central capability that users may never notice, yet administrators and business leaders may greatly appreciate.

People continue attaching and opening documents from the records they work with every day. Business Central continues providing the business context. The external service provides the file storage.

For companies that expect document volumes to grow, this is worth considering early rather than waiting until database capacity becomes an urgent problem.

Take a few minutes to review the official Microsoft Learn guidance for storing Business Central document attachments externally. Then ask your team one practical question: Where should our business documents live, and who will be responsible for protecting them?

If your organisation is implementing Business Central, reviewing its storage architecture or trying to manage a growing volume of attachments, contact channel@4sight.cloud. The 4Sight team can help you assess the available options, choose an appropriate storage approach and plan the configuration around your operational and governance requirements.

Official reference

Microsoft Learn: Store Business Central document attachments in external file storage