I need to add purchase tax to QBO for our Spanish entity

Hello there, kalea-belso-thei.

I can guide you on where to add purchase tax in QuickBooks Online. 

We can set up a custom tax from the Taxes page and then choose the This tax is collected on purchases option to include the sales tax when creating a bill.

Here's how:

1. Click on Taxes at the left pane and then select Add tax.
2. Choose Custom tax.
3. Fill out all the fields needed in the Add tax panel. Place a checkmark for This tax collected on the purchases option.
4. Enter the rate in the Purchase rate field.
5. Place a checkmark for Purchase tax is a reclaimable option if it is reclaimable.
6. Click Save.

If you need further guidance regarding the setup? Please refer to this article: How do I set up sales GST/VAT rates and use them on forms? (International QBO)

On top of that, you can review these handy resources if you need more insights about VAT: Setup VAT in QuickBooks Online.

I'm just a post away if you have any other concerns about adding purchase tax in QBO. Have a great day ahead!