Why multiple hosting causes 6073-816: QB's multi-user architecture requires exactly one computer to act as the host — the server. The host's QB Database Server Manager (QBDSM) controls all file access and arbitrates between users. When multiple computers each have hosting enabled (File → Utilities → Host Multi-User Access is active on more than one machine), each QBDSM instance tries to claim control of the company file simultaneously. This creates a conflict — QB can't determine which QBDSM is authoritative and reports -6073, -816. The fix is straightforward: only the server should have hosting enabled. All workstations must be in "Stop Hosting Multi-User Access" state.

Multiple Computers Hosting Simultaneously

Primary cause — more than one machine has "Host Multi-User Access" enabled. This commonly happens when QB is installed on a new workstation and the default install enables hosting, or when the original host computer was changed but the old workstation still has hosting active. QB can only have one host — any additional hosts conflict and produce -6073.

Firewall Blocking QB Ports

Even with correct hosting, if the firewall blocks QB's required ports (8019 for QBDSM, and dynamic ports 56728–56730), workstations can't communicate with the server's QBDSM. QB reports -6073, -816 when the network connection to the host QBDSM is blocked. Configure firewall exceptions for these specific ports.

Corrupted .ND File Alongside Hosting Conflict

If the Network Data (.ND) file is corrupted while a hosting conflict exists, -6073, -816 appears on every access attempt even after disabling extra hosts. The .ND stores the server's network information and must be rebuilt after resolving the hosting conflict. Rename .ND → .OLD and run QBDSM scan.

Hosting Migration — Old Host Still Active

When a business moves from one server to another, the old server's QB often retains hosting enabled. If both old and new servers are on the network simultaneously with hosting active, -6073 appears. The old server's QB must be set to "Stop Hosting Multi-User Access" or QB should be uninstalled from the old server.

New QB Install on Workstation with Default Hosting

When QB is freshly installed on a workstation, it sometimes defaults to hosting enabled. If that workstation joins an existing multi-user network where a server already hosts the file, a conflict immediately arises. On every new QB workstation install, verify that hosting is set to "Stop Hosting Multi-User Access" before connecting to the network.

Company File Stored on External Drive or Cloud-Sync Folder

If the company file is on a USB drive, external HDD, or a OneDrive/Dropbox sync folder, multiple access points can conflict. Sync software can create read/write conflicts that QB interprets as multiple hosting. Move the company file to a local drive on the server.

METHOD 1 Verify and Fix Hosting on All Machines Resolves the multiple-hosting cause directly

METHOD 2 Rename .ND and .TLG + QBDSM Scan Corrupted .ND from the hosting conflict

METHOD 3 Configure Firewall Ports for QB Multi-User Firewall blocking QBDSM communication

METHOD 4 Run File Doctor + Move File off External/Cloud Drive File damage or wrong storage location

How do I check if multiple computers have hosting enabled?

Go to each computer that has QuickBooks installed, open QB (or try to open it if the error prevents it), then go to File → Utilities. Look at the menu option: if it says "Stop Hosting Multi-User Access" — hosting is active on this machine. If it says "Host Multi-User Access" — hosting is not active. On a 10-machine network, check all 10. Only the server should show "Stop Hosting Multi-User Access." Every other machine should show "Host Multi-User Access" (meaning you would click it to turn hosting on — but don't, as it's correctly off). If any workstation shows "Stop Hosting," click it to disable hosting on that machine.

How is Error 6073 different from Error 6189?

They're related but distinct. Error 6189, -816 is specifically a QBDSM network configuration issue — QBDSM can't find or reach the company file over the network (often because the QBDSM .ND file is wrong, the server hostname changed, or QBDSM isn't installed on the server). Error 6073, -816 is specifically a multiple-hosting conflict — the issue isn't that QBDSM can't find the file, but that two QBDSM instances are competing for control of the same file. The key diagnostic: if you see -6073 and check the machines and find hosting is active on multiple, you have the 6073 situation. If you check and only the server has hosting but the error persists, it's more likely 6189.

Can I store the QuickBooks company file on OneDrive or Dropbox?

Intuit's official recommendation is no — QuickBooks company files should not be stored in real-time sync folders like OneDrive, Dropbox, or Google Drive. These sync services keep the file constantly read/write active in the background, which conflicts with QB's own file locking mechanism. QB writes lock files and transaction logs constantly during operation, and a sync service attempting to upload changes at the same time creates conflicts that QB reports as -6073, -816, or other 6000 series errors. If you need cloud access to QB, use a cloud-hosted QB solution (like QB Online or a hosted QB service) rather than storing Desktop QB files in a sync folder.