Can QuickBooks Desktop import an IIF file to adjust inventory quantities (Inventory Adjustment)?

You need to use an importer tool to do so. You can prepare your data with the following template

then purchase TP Importer to proceed. It's a $199 one time license.

https://get.transactionpro.com/qbd

If your company is located in the US, you can get the license for free from a partner. Contact @Fiat Lux - ASIA via email directly for details.

Greetings, justin00195.

It seems you've posted twice in the Community forum about your concern with the IIF file, which my colleague Tori B  already answered.

To view the response, check out this link: https://quickbooks.intuit.com/learn-support/en-us/other-questions/re-can-quickbooks-desktop-import-a....

Have more questions about managing your inventory? Visit our Community Forum for expert help. Our team is ready and waiting to provide all the support you need. 

Yes, this is possible. QuickBooks can import inventory adjustments for quantity adjustments, value adjustments, or both.

You can use our BRC IIF Transaction Creator Pro to do it, or at least use it to figure out the IIF file format for these transactions. It can be download in trial mode - no charge. You might even like using it instead of writing your own IIF files, which can be rather complicated.