Just wanted to bring something to your attention you may not be aware regarding Quickbooks Online integration:

NOTE: This is not an issue on the Artcloud side of integration. It's a QBO issue.

I tried to do a test integration with a couple of our existing AC invoices into QBO. I received the attached error message and could not proceed into importing my CSV. I got on with support and it turns out that the smaller QBO account types will not allow importing if sales tax is set up in QBO. Additionally, in QBO, there’s no easy way to simply turn off sales tax if it was already set up and other invoices were issued.

The QBO upper tier accounts allow it, so the programming exists within their system. I’ve sent a feedback request for them to set it up for the lower tiers. Not sure if you have any push you can give, but it certainly would be helpful for your voice to also be heard since your company is working with numerous other businesses that use QBO and probably are in the same boat as us.