A client cannot pay invoices greater than $700 because his bank (in Sweden) demands 3DS authentication. Does Quickbooks offer that? How do I set that up?

Do you need to accept that payment by QB Payments? Afaik, QB Payment doesn't allow to accept international payments. You will need a 3rd party solution to do so. 

Hi there, CarlosAllende. 

Let me share some insights into why your clients cannot pay invoices in QuickBooks Online (QBO). 

I agree with Fiat-Lux Asia. The option to Pay the invoice using an International bank is currently unavailable in QuickBooks Online (QBO). I suggest looking for a 3rd-party app that can integrate with QBO to allow your international clients to pay online using an international bank. To do this, you'll need to go to the Apps inside QuickBooks Online.

Here's how:

1. Click Apps in the left navigation menu.
2. Search for the keyword in the search bar.
3. Select the app you want to integrate and review the app if it is what you're looking for.
4. Click Get App Now and complete the following on-screen instructions.

For future reference on how to process an ACH bank transfer for your customer’s sales receipt or invoice in QuickBooks Online, please check this article: Process an ACH bank transfer from a customer.

I've also provided this article to learn about 3D Secure: 

• 3-D Secure Overview
• 3-D Secure History

You're always welcome to post a reply if you need further assistance with paying invoices in QBO. I'll keep an eye on this thread. Have a great day!