Understanding QuickBooks File Types (.QBW, .QBB, .QBM, .TLG)

Why File Types Matter

QuickBooks Desktop creates and relies on a family of interconnected files, each serving a distinct purpose. Most users only interact with their company file directly, but understanding the full ecosystem of file types gives you a real advantage when it comes to backups, troubleshooting, and working with your accountant. It also matters when things go wrong — knowing which files to send for repair, which to delete safely, and which to protect at all costs can be the difference between a quick fix and a painful data loss.

This guide covers every QuickBooks file type you’re likely to encounter, explains what each one does, and tells you which ones are critical to protect.

.QBW — The Working Company File

The .QBW file is your actual QuickBooks company file. This is the live database where all of your financial data resides: your chart of accounts, every transaction you’ve ever entered, your customer and vendor lists, inventory records, payroll data, memorized transactions, and every report QuickBooks can generate. When you open QuickBooks and work in your company, you’re working directly in the .QBW file.

Because the .QBW is a live database, it’s also the file most susceptible to corruption. Power outages during a save operation, network interruptions in multi-user mode, and hardware failures can all damage the .QBW at the moment data is being written. This is exactly why backups exist — and why understanding the backup file types below is so important.

File sizes for .QBW files vary enormously depending on your business volume and history. A small business with a few years of data might have a 50 MB file, while a mid-size company running Enterprise with a decade of transactions can easily reach 1 GB or more. File size directly impacts QuickBooks’ performance: files under 200 MB typically run smoothly, while files over 500 MB start to slow down noticeably, particularly when running reports or scrolling through large lists.

If your .QBW file has become too large and is causing performance problems, a SuperCondense service can dramatically reduce its size while preserving your working data.

.QBB — The Backup File

A .QBB file is a compressed backup of your entire company file, created through File > Back Up Company > Create Local Backup. It packages your .QBW data along with supporting files (including the transaction log) into a single compressed archive. To use a .QBB file, you must restore it through QuickBooks, which decompresses it and recreates a working .QBW file.

The .QBB format is the standard for QuickBooks backups and the format you should use for your regular backup routine. It preserves everything: all financial data, templates, logos, memorized reports, letter templates, and preferences. The compression typically reduces the file to 50-70% of the original .QBW size.

One important detail: you cannot open a .QBB file directly in QuickBooks. You must go through the restore process (File > Open or Restore Company > Restore a Backup Copy), which creates a new .QBW from the backup. This is by design — it prevents accidentally working in a backup file and getting confused about which file contains your current data.

When sending a file for professional repair, a .QBB backup is the second-best option (after a .QBM portable file) because it contains a complete snapshot of your data.

.QBM — The Portable Company File

A .QBM (portable company file) is a heavily compressed version of your company file, created through File > Create Copy > Portable Company File. Portable files strip out everything except the core financial data — your chart of accounts, lists, and transactions — while dropping templates, logos, letter formats, and other non-essential elements.

The result is a dramatically smaller file, often 60-80% smaller than even a .QBB backup. A 500 MB .QBW file might produce a 100 MB .QBB backup but only a 40-50 MB .QBM portable file.

Portable files are designed for transferring data between locations. They’re ideal for sending to your accountant, uploading to a repair service, or moving between computers. Like .QBB files, a .QBM must be restored through QuickBooks before it can be used — the restore process recreates a full .QBW from the portable data.

Because of their small size and data-focused content, .QBM files are our preferred format when customers need to upload files for repair. They contain all the financial data we need while being much faster to upload and download. If you’re sending a file to us for file repair, creating a portable copy is the best option when your QuickBooks file can still be opened.

The trade-off is that a .QBM doesn’t include everything. Templates, logos, and some customizations will need to be re-applied after restoring from a portable file. For this reason, a .QBM should supplement your backup strategy, not replace it.

.TLG — The Transaction Log

The .TLG (Transaction Log) file sits alongside your .QBW file in the same folder and records every transaction entered since your last backup. QuickBooks maintains this file automatically — you don’t create or manage it directly. Each time you create a backup, the .TLG resets and begins recording new transactions from that point forward.

The .TLG serves as a bridge between your last backup and the current state of your data. If your .QBW becomes corrupted and you need to restore from a backup, the .TLG can potentially be used to replay the transactions that occurred after the backup was created, recovering work that would otherwise be lost.

This makes the .TLG extremely valuable in disaster recovery scenarios. Our TLG data recovery service specializes in extracting transaction data from .TLG files when the .QBW is beyond repair and the most recent backup is outdated. While not every transaction can always be recovered from a .TLG, it’s often the best available source of recent data.

The critical thing to understand about .TLG files is that they are not a replacement for backups. The .TLG is only useful in combination with a .QBB or .QBW to restore from. On its own, a .TLG doesn’t contain enough information to reconstruct a complete company file.

.QBX and .QBA — Accountant’s Copy Files

The Accountant’s Copy system is a workflow that allows your accountant to make changes to your file (adjusting entries, reclassifying transactions) while you continue entering day-to-day transactions, and then merge both sets of changes back together.

The .QBX file is the export you send to your accountant. It’s created through File > Accountant’s Copy > Client Activities > Save File, and it contains a copy of your data up to a “dividing date” you specify. Your accountant opens the .QBX in their copy of QuickBooks, makes their adjustments, and saves the result as a .QBA file.

The .QBA file is what your accountant sends back. You import it through File > Accountant’s Copy > Client Activities > Import Accountant’s Changes, and QuickBooks merges their adjustments into your working file.

While the Accountant’s Copy workflow is active, you’ll have restrictions on what you can change in your file for dates before the dividing date. This prevents conflicts between your changes and the accountant’s changes.

These files are typically managed through the accountant’s workflow and you won’t interact with them outside of that context.

.ND and .DSN — Network Descriptor Files

The .ND (Network Descriptor) file is created by the QuickBooks Database Server Manager and contains information about the host computer serving the company file in a multi-user environment. The .DSN file serves a similar role for ODBC database connections.

These are small configuration files that sit in the same directory as your .QBW file. They do not contain any financial data. Their only purpose is to help QuickBooks locate and connect to the company file over a network.

The reason these files matter to you is that they are a common source of connection errors. When an .ND file becomes corrupted or contains stale information (for example, after moving the company file to a different computer), QuickBooks may throw -6000 series errors or H-series multi-user errors. Deleting the .ND file is a safe first step in troubleshooting these errors — QuickBooks will automatically recreate it the next time the Database Server Manager scans the file.

File Size and Performance Implications

Understanding how file sizes relate across types helps you plan your storage and backup strategy. As a general rule, if your .QBW is 500 MB, expect your .QBB to be around 300-350 MB and your .QBM to be around 40-80 MB. Your .TLG will grow continuously between backups and can reach significant sizes if backups are infrequent — we’ve seen .TLG files larger than the .QBW itself in businesses that haven’t backed up in months.

For backup storage planning, budget for at least 5 copies of your .QBB file across multiple locations. For file transfers (sending to an accountant or repair service), use .QBM whenever possible to minimize upload time. And when calling for support, having the file size of your .QBW (visible on the F2 Product Information screen or by right-clicking the file in Windows Explorer) helps your service provider give you accurate pricing and timelines.

Frequently Asked Questions

Which files should I include in my backup routine?

Your primary backup through QuickBooks (the .QBB file) automatically includes the essential data. Beyond that, it’s wise to also save a copy of your .TLG file separately as an extra safety net. The .ND and .DSN files don’t need to be backed up — they’re recreated automatically. If you’ve customized templates, logos, or memorized reports extensively, a .QBB backup preserves those; a .QBM does not.

Can I rename QuickBooks files?

You can rename .QBB and .QBM files freely — they’re self-contained archives that don’t depend on their filename. Renaming a .QBW file is safe but requires that you also delete the associated .ND and .TLG files so QuickBooks can recreate them with the new name. Never rename a .QBW while QuickBooks has it open or while other users are connected in multi-user mode.

What happens if I delete the .TLG file?

Deleting the .TLG file does not affect your company file or your ability to work in QuickBooks. QuickBooks will simply create a new .TLG and start recording transactions from that point forward. However, you lose the ability to recover transactions between your last backup and the moment of deletion. If your .QBW is currently working fine and you have a recent backup, deleting an oversized .TLG is safe. If there’s any chance you might need those transactions, keep the .TLG until you’ve confirmed your data is intact.

Which file type should I send for professional repair?

In order of preference: a .QBM portable file is ideal because it’s the smallest and fastest to upload while containing all the financial data needed for repair. A .QBB backup is the next best option. A zipped copy of the .QBW file works when QuickBooks won’t open (making .QBM and .QBB creation impossible). If your file is severely corrupted, sending both the .QBW and its associated .TLG gives the repair team the most data to work with.

Can I open a .QBB or .QBM file directly without restoring?

No. Both .QBB and .QBM files must be restored through QuickBooks (File > Open or Restore Company) before they can be used. The restore process decompresses the data and creates a new .QBW working file. This is an intentional design choice — it prevents you from accidentally working in a backup file and falling out of sync with your actual company data.