Quickbooks File Repair — C=79 (problem with inventory data)

QuickBooks error C=79 is raised when QuickBooks finds a problem inside your inventory data and cannot reconcile what your item records claim against the transactions that move stock. Intuit classes it as a recoverable error, which means the underlying figures usually still exist and can be repaired -- the file is reporting an inconsistency, not announcing that the data is gone.

Why inventory data is fragile

Inventory is one of the most interconnected parts of a QuickBooks file. Each item carries a quantity on hand and an average cost that QuickBooks recalculates every time you buy, sell, build, or adjust stock. Those values are derived from a long chain of linked transactions, so a single broken link -- one bad item receipt or a half-saved adjustment -- can throw the whole calculation off and produce C=79.

Symptoms you'll typically see

• Negative quantities on hand for items you know are in stock.
• Inventory valuation reports that do not tie out to the balance sheet inventory account.
• The error firing when you save a build, invoice, or inventory adjustment.
• Average cost figures that shift without an obvious cause.

What you can safely try first

Stop posting new inventory transactions and copy the file before troubleshooting. Then, on the copy:

• Run File > Utilities > Verify Data to confirm QuickBooks sees the inventory damage, then Rebuild Data if it does.
• Hunt down any items showing negative quantity and correct them, since negatives are a frequent root cause.
• Check the date order of recent stock movements -- a back-dated adjustment can break the cost chain.
• Restore a clean .QBB backup from before the error if you have one available.

When professional recovery is the safer path

Verify and Rebuild repair some inventory faults, but when the item-to-transaction links are badly broken they can drop transactions or leave valuation still out of balance -- and running them repeatedly compounds the damage. If C=79 keeps returning, hand the file to our team. Our engineers repair the inventory structures at the record level, reconcile quantities and costs, and return a verified working file. All work is done in-house in North America, backed by a no-data, no-charge guarantee. Learn how QuickBooks data recovery works, or start a recovery.