Part of your QuickBooks company data is the TLG file. It’s not something you normally are aware of, but in some situations it can be a very important file.

The transaction log file (TLG for short) is maintained automatically by QuickBooks as part of your data. The file resides in the same folder as your main QBW file, and has the same file name. But it has a .TLG extension. In transaction-intensive businesses, the file can become quite large — 1GB or bigger.

Whenever you post a transaction in your company file, the TLG file is updated. And that is why it is sometimes a very valuable file.

We sometimes talk to people who have lost their current data file — it either got deleted somehow, or is so badly damaged it is unusable and unfixable.

But if they have a good backup — even if it is old — and a good current TLG file, we can take the old backup and bring it to current status by applying the missing transactions we can get out of the TLG file.

It’s one method we use for QuickBooks data repair.

I am working with a customer today who has this exact scenario, so I thought I’d briefly write about it.

p.s. We occasionally hear of users being instructed to delete their TLG file. Don’t ever do that without copying it to a different folder or drive first. You might need it sometime!

Have you ever seen a screen like this?

I hope not!

But if you ever do find yourself unable to open your company, or it fails when you try to do certain operations in QuickBooks, there are three possibilities for recovery:

1. Restore your last good backup. Hopefully you have one that is pretty current.

Just make sure that you copy off your bad version of the data before you restore. Sound strange? Once you restore, your backup will overwrite your current data — that’s a permanent thing. So copy your bad version of the QBW file to a different location before restoring, just to keep all your options open.

If option #1 is unavailable or impractical for you…

2.  Upload your damaged file to for repair. We have corrected over 10,000 damaged accounting databases since the 1980s, and our success rate with damaged QuickBooks data files is 95%.

If your QBW file is hopelessly corrupted, or is somehow even missing…

3. Upload your last good backup — even if it’s old — and your current TLG file.  The TLG file is your transaction log file and has the same name as your QBW file, but has a TLG extension. We can take your old backup and your current TLG file and bring your old backup up to date.

Most users never encounter this problem. But if you do, at least you have some options.

There are some QuickBooks data situations that have good endings, and some that don’t.


  • -6000 errors. If you get a 6000 error when you try to open your company file, most of the time if means that your data is corrupted, but most of the time, it is also repairable.
  • “Connection to database lost” errors. Ditto above.
  • Errors triggered when accessing particular accounts or transactions. Same.
  • Failures during upgrades, backups, verifies, rebuilds. We can fix these.
  • For pre-2006 QuickBooks versions, c-342, c-43, c-44 errors are almost always repairable.


  • -6150 errors. This error usually indicates hopeless file corruption. A critical area of the file has become damaged that is not reconstructable. Although this error indicates that the QBW file is unrecoverable, we can still help you if you have an old but good backup and a current TLG file.
  • Files recovered from damaged or reformatted hard drives. This situation is common, but unfortunately, does not usually have a good outcome for data repair. Files recovered from damaged or reformatted HDs, or undeleted from drives, often have random contents — not the original QuickBooks data that was there in the first place. I don’t know why that is, but I’ve talked to a lot of users and IT people over the years with this situation, and that seems to be the case about 90% of the time that people contact us.

A quick way to test the recoverability of a file recovered from bad media is to zip the recovered file with WinZip or Windows folder compression. In a lot of cases, the file will zip up 99%. For example, a 100MB QBW file will zip down to 1MB. That indicates that the original contents of the file did not get recovered properly, and you ended up with a QBW file full of zeroes.