All of my inventory has been entered incorrectly. How do I fix the quantity without receiving bad debt or inventory shrinkages?

Hello there, UserLE. 

Sometimes you might see that you have either more or fewer of an item than QuickBooks shows. If you track inventory in QuickBooks Online Plus and Advanced, we can manually adjust an item's quantity without recording a purchase or sale, to match what you actually have in stock.

However, when you save the inventory adjustment, we automatically record appropriate adjustments to your stock Asset and Cost of Goods Sold (under stock Shrinkage) accounts for our reports to be accurate. You can check this article for more details: Adjust inventory quantity on hand in QuickBooks Online.

On the other hand, we have the option to delete and recreate the items entering the correct quantity on hand. Set up and track your inventory in QuickBooks Online. 

I'm here if you have other questions. Take care!

@UserLE 

in the chart of accounts, open the register for inventory asset

each line that has a START notation is the starting stockage entry for that item, edit them as needed

There are a number of reasons for inventory shrinkage. Inventory shrinkage can take place when items, such as expired produce, are naturally no longer sellable. Or, shrinkage might be due to damaged items.

Inventory shrinkage may also be the result of errors. You or one of your employees might miscount items. Your vendor might also make errors when they supply you with inventory items.

In some cases, you might have inventory shrinkage because of malicious actions, such as theft, shoplifting, or fraud. Vendors may commit fraud and give you less inventory than what you purchased. Or, employees might steal inventory. Shrinkage is also common when customers shoplift from your business.

A shrinkage expense account will be recorded under the Cost of Goods Sold (COGS) It includes material cost, direct labor cost, and direct factory overheads, and is directly proportional to revenue. As revenue increases, more resources are required to produce goods or services. COGS is often an account.