Let me show you how to update your inventory items, @ZeirnaV.

Yes, you can enter an inventory quantity adjustment without recording a purchase or sale to match what you have in stock.

This feature is available if you're subscribed to either QuickBooks Online Plus or Advanced.

You can follow the steps below on how to add an inventory quantity adjustment:

1. Go to the + New button and tap Inventory Qty Adjustment. 
2. On the Inventory Quantity Adjustment page that appears, set the Adjustment Date.
3. Proceed to the Inventory adjustment account drop-down and select the appropriate account.
4. Enter the products in the Product field drop-down. 
5. Provide a new quantity or a change in quantity.
6. Click Save and close once you're done. 

Here's the adjust inventory quantity on hand in QuickBooks Online article for more information. 

Also, here’s more information on how to enter product and service items you buy and sell: Add product and service items to QuickBooks Online.

I'm always here if you have follow-up questions about inventory management. Take care and have a wonderful day!